JP4898000B2 - Absorbing member comprising a large surface area material for absorbing bodily fluids - Google Patents

Description

【０１７９】
【表２】

【０１８０】
【表３】

【０１８１】
上記の簡単化された例に対する平衡取り込み量は０．３１８ｇである。
下記は平衡取り込み量を決定するために使用されたＣ言語でのコードである。
【０１８２】
【表４】

【０１８３】
毛管吸着パラメータ
負荷の説明（閉じ込め圧力）：０．２ｐｓｉ負荷
平衡試料（ｎ）：５０
平衡定数：０．０００５ｇ／ｓｅｃ
セットアップ高さ値：１００ｃｍ
最終高さ値：０ｃｍ
静水頭パラメータ：２００，１８０，１６０，１４０，１２０，１００，９０，８０，７０，６０，５０，４５，４０，３５，３０，２５，２０，１５，１０，５および０ｃｍ
毛管吸着吸収容量の測定のために、上記で規定した全ての高さを上述した順序で用いて、毛管吸着試験手順を実施する。特定高さ（たとえば３５ｃｍ）での毛管吸着吸収容量を測定することが望ましい場合でも、一連の静水頭パラメータ全体を規定された順序で完了しなければならない。試験試料に対する毛管吸着等温線を生成するための毛管吸着試験の実施において、これら高さを全て使用しているけれども、本発明の開示では２００，１４０，１００，５０，３５および０ｃｍの特定高さでのそれらの吸収特性に基づいて貯蔵吸収部材を説明する。
【０１８４】
毛管吸着試験手順
１）実験準備手順に従う。
【０１８５】
２）恒温槽２０８がオンで、水がガラスフリット２０２を通って循環しており、ガラスフリットディスク２６０の温度が３１℃であることを確認する。
【０１８６】
３）ガラスフリット２０２を２００ｃｍの吸引高さに配置する。ガラスフリット２０２をはかり付き液体リザーバ２０６と接続するためにストップコック２０９および２１０を開く（ストップコック２１０は液体リザーバ２０５に対して閉じる。）ガラスフリット２０２を３０分間かけて平衡にする。
【０１８７】
４）上記の毛管吸着パラメータをコンピュータに入力する。
【０１８８】
５）ストップコック２０９および２１０を閉じる。
【０１８９】
６）ガラスフリット２０２をセットアップ高さ１００ｃｍへ移動させる。
【０１９０】
７）テフロン（登録商標）リング２６２をガラスフリットディスク２６０の表面上に置く。Ｏリング２６４をテフロン（登録商標）リング上に置く。予備加熱したシリンダ２６６をテフロン（登録商標）リング上に同心状に置く。試験試料２７０をガラスフリットディスク２６０上のシリンダ２６６に同心状に置く。ピストン２６８をシリンダ２６６内に置く。必要であれば、追加の閉じ込め用おもりをピストンチャンバ２９０内に置く。
【０１９１】
８）ガラスフリット２０２を穴開きフィルムで被覆する。
【０１９２】
９）この時点でのはかり読み取り値がゼロまたは自重読み取り値を確定する。
【０１９３】
１０）ガラスフリット２０２を２００ｃｍへ移動させる。
【０１９４】
１１）ストップコック２０９および２１０を開き（ストップコック２１０は液体リザーバ２０５に対しては閉じる）、はかりおよび時間の読み取りを開始する。
【０１９５】
ガラスフリット補正（ブランク補正取り込み量）
ガラスフリットディスク２６０は多孔質構造体であるので、ガラスフリット（２０２）の毛管吸着吸収取り込み量（ブランク補正取り込み量）を測定し、真の試験試料の毛管吸着吸収取り込み量を得るために差し引かなければならない。ガラスフリット補正は、使用される各々の新しいガラスフリットについて実施する。試験試料を使用しないこと以外は上記の通りに毛管吸着試験手順を実行して、ブランク取り込み量（ｇ）を得る。各々の規定高さでの経過時間がブランク時間（ｓ）に等しい。
【０１９６】
蒸発損失補正
１）ガラスフリット２０２をゼロの２ｃｍ上方へ移動させ、ストップコック２０９および２１０を開いて（リザーバ２０５に対して閉じて）、これをこの高さで３０分間かけて平衡にする。
【０１９７】
２）ストップコック２０９および２１０を閉じる。
【０１９８】
３）テフロン（登録商標）リング２６２をガラスフリットディスク２６０の表面上に置く。Ｏリング２６４をテフロン（登録商標）リングの上に置く。予備加熱したシリンダ２６６をテフロン（登録商標）リング上に同心状に置く。ピストン２６８をシリンダ２６６内に入れる。穴開きフィルムをガラスフリット２０２上に置く。
【０１９９】
４）ストップコック２０９および２１０を開いて（リザーバ２０５に対して閉じて）、３．５時間にわたってはかりの読み取りおよび時間を記録する。試料の蒸発量（ｇ／ｈｒ）を下記のように計算する。
【０２００】
［１時間ではかり読み取り−３．５時間ではかり読み取り］／２．５時間
上記の予防措置の全てを取った後でも、いくらかの蒸発損失、試験試料およびフリット補正両方について典型的にはおおよそ０．１０ｇ／ｈｒの蒸発損失が発生するであろう。理想的には、試料の蒸発は各々の新たに据え付けられたガラスフリット２０２について測定する。
【０２０１】
装置の洗浄
ガラスフリット２０２を新たに据え付けたときには新しいＴｙｇｏｎ（登録商標）チューブ２０３を使用する。ガラスチューブ２０４および２１１、液体リザーブ２０５、およびはかり付き液体リザーバ２０６は、細菌汚染が目に見える場合には、５０％Ｃｌｏｒｏｘ Ｂｌｅａｃｈ（登録商標）／蒸留水を用いて洗浄した後、蒸留水ですすぎ洗いする。
【０２０２】
ａ．各実験後の洗浄
各実験の終了時に（試験試料を取り除いた後）、液体リザーバ２０５からの２５０ｍＬの試験液により、ガラスフリットをフォワードフラッシュ（すなわち、試験液をガラスフリットの底部へ導入する）して、ガラスフリットディスクの孔から残留試験試料を除去する。ストップコック２０９および２１０を液体リザーバ２０５に対して開き、はかり付き液体リザーバ２０６に対して閉じ、ガラスフリットをその支持具から取外し、上下を逆さまにして最初に試験液によりすすぎ洗いし、次にアセトンおよび試験液によりすすぎ洗いする。すすぎ洗い中、ガラスフリットは上下を逆さまに傾けなければならず、すすぎ液はガラスフリットディスクの試験試料接触面上へ噴出させる。すすぎ洗い後、ガラスフリットを２５０ｍＬの合成尿により２度のフォワードフラッシュする。最後に、ガラスフリットを支持具に再び取り付け、フリット表面を水平にする。
【０２０３】
ｂ．ガラスフリット性能のモニター
ガラスフリットの性能を、各洗浄手順後および各ガラスフリットを新たに取り付ける毎に、０ｃｍ位置でのガラスフリットセットアップでモニターしなければならない。５０ｍＬの試験液を水平にしたガラスフリットディスク表面（テフロン（登録商標）リング、Ｏリングおよびシリンダ／ピストン部品なし）上に注ぐ。試験液レベルがガラスフリットディスク表面の上方５ｍｍへ下がるのに要する時間を記録する。この時間が４．５分間を超える場合には、定期的洗浄を実施しなければならない。
【０２０４】
ｃ．定期的洗浄
定期的に（上記のフリット性能のモニターの項を参照）ガラスフリットを完全に洗浄しては目詰まりを防止する。すすぎ液は蒸留水、アセトン、５０％Ｃｌｏｒｏｘ Ｂｌｅａｃｈ（登録商標）／蒸留水（細菌増殖を除去するため）および試験液である。洗浄には、支持具からガラスフリットを取り外すことおよびすべてのチューブを取り外すことが含まれる。フリットを上下逆にし、適切な液体および量により、を下記の順序で、ガラスフリットをフォワードフラッシュする（すなわち、試験液をガラスフリットの底部に導入する）。
【０２０５】
１．２５０ｍＬの蒸留水
２．１００ｍＬのアセトン
３．２５０ｍＬの蒸留水
４．１００ｍＬの５０：５０Ｃｌｏｒｏｘ（登録商標）／蒸留水溶液
５．２５０ｍＬの蒸留水
６．２５０ｍＬの試験液
ガラスフリットの性能が流量の設定基準（上記参照）内にあり、ガラスフリットディスク表面上に残留物を観察できない場合には洗浄手順は申し分がない。洗浄を良好に実施できない場合は、フリットを交換しなければならない。
【０２０６】
計算
各規定高さで、毛管吸引高さ（ｃｍ）、時間、および取り込み量（グラム）からなるレポートを与えるように、コンピュータをセットアップする。このデータから、フリット取り込み量および蒸発損失の両方について補正された、毛管吸引吸収容量を計算できる。また、０ｃｍでの毛管吸引吸収容量に基づいて、規定高さでの毛管吸収効率を計算できる。さらに、２００ｃｍでの初期有効取り込み速度が計算される。
【０２０７】
ブランク補正取り込み量
ブランク補正取り込み量（ｇ）＝ブランク取り込み量（ｇ）−ブランク時間＊試料蒸発量（ｇ／ｈｒ）／３６００（ｓ／ｈｒ）
毛管吸引吸着容量（「ＣＳＡＣ」）：
ＣＳＡＣ（ｇ／ｇ）＝{試料取り込み量（ｇ）−（試料時間＊試料蒸発量（ｇ／ｈｒ）／３６００（ｓ／ｈｒ））−ブランク補正取り込み量（ｇ）}／試料の乾燥重量（ｇ）
２００ｃｍでの初期有効取り込み速度（「ＩＥＵＲ」）
ＩＥＵＲ（ｇ／ｇ／ｈｒ）＝２００ｃｍでのＣＳＡＣ（ｇ／ｇ）／２００ｃｍでの試料時間（ｓ）。
【０２０８】
レポート
所定の吸収部材または所定の大表面積材料について毛管吸着吸収容量を計算するために、各試料について最低２回の測定値を採取し、各々の高さで取り込み量を平均化しなければならない。
【０２０９】
Ｂ．垂直吊下げ吸着高さ（ＶＨＳＨ）
適当な長さ（典型的には少なくとも６０ｃｍ）で典型的には約１ｃｍの幅を持つ発泡体のストリップを選択することにより、垂直吊下げ吸着高さ（「ＶＨＳＨ」）試験を達成する。ストリップを吊り下げるためのクリップを用い、このストリップを３１℃に温度調節されたチャンバー内に吊り下げる。ストリップの底部を、やはり３１℃の試験液に浸す。試験液は、１９９７年２月４日発行の米国特許第５，５９９，３３５（Ｇｏｌｄｍａｎら）（その開示は参照により本明細書に組み込まれている）に記載されているような合成尿が好ましい。長時間かけて、試験液はストリップを吸い上がり、もはや全く吸い上げが起こらない平衡点に達するであろう。平衡点の決定を容易にするために、試験液を乾かしてもよい。たとえば、試料をガラスチューブ（ガラスは試料に接触しない）の中に入れ、試料チューブを適切にキャップした状態を維持することにより、試料からの蒸発を防止するように注意しなければならない。本発明の材料について平衡に達するのに要する時間は変化することがあり、約２４時間から９６時間、またはそれ以上の範囲である。１時間にわたって吸い上げ液の高さに認識できる変化がない場合には、平衡が達成されたとみなされる。
【０２１０】
その中に保持されている液体がしぼり出されるのを避けるよう注意しながら、試験ストリップを試験チャンバーから取り出す。ストリップから長さ２．５ｃｍの複数の切片を切り出し、各切片を秤量する。便宜上、完全に膨張した高さの約５０％以下の初期切片は、長さ２インチ（５．１ｃｍ）の切片に切り出してもよい。これらの重量を発泡体のオーブン乾燥重量で割って、発泡体の種々の多価sでの容量（ｇ／ｇ）を計算する。切片が採取された高さに対する容量のチャートを図表にすることにより、図５に図示されているようなグラフを展開することができる。Ｘ％でのＶＨＳＨ高さは、発泡体中で０ｃｍ容量（またはＦＡＣ）のＸ％が保持されている場合の高さ（ｃｍ）である。重要な代表値は９０％でのＶＨＳＨである。原理的には、Ｘはいかなる値でもよい。ＶＨＳＨに対する最も再現性のある測定は、発明者らの経験の範囲内では、Ｘ＝９０％で達成される。当業者には、この一点での数値が高さに対する容量のプロットで得られる曲線の形状を十分に表すわけではないことは明らかである。しかし、この一点は本発明の発泡体についての実際的な比較点として役立つ。
【０２１１】
【実施例】
VII．代表例
例１
ガラス超極細繊維を含む貯蔵吸収部材
この例では、ヒドロゲル形成吸収性ポリマーと、従来のエアーデポジションプロセスよりも高い密度と構造組織化のためにウェット・エンド成形プロセスを使用して形成された大表面積ガラス超極細繊維とを含む高毛管吸引吸収部材について説明する。ガラス超極細繊維マトリックス中の吸収性ポリマーの分布が均質に近いような、ヒドロゲル形成吸収性ポリマーを含有する部材を構成するために下記の手順に従う。
【０２１２】
４．０ｇのＡＳＡＰ２３００（イリノイ州アーリントンハイツのアメリカン・コロイド社(American Colloid Co.)の子会社であるケムダル(Chemdal)ＬＴＤから入手可能；また、オハイオ州シンシナティのザ・プロクター＆ギャンブル社(The Procter & Gamble CO.)の紙テクノロジー事業部からも入手可能）および４．０ｇのガラス超極細繊維（コロラド州デンバーのマンヴィル・セイルズ社(Manville Sales Corp.)から「Ｑ−ファイバー(Q-FIBERS)，コード１０８，１１０バルク」として入手可能）の混合物を、約５００ｍＬの３Ａアルコール（９５％エタノール、５％メタノール）、またはイソプロパノールもしくは類似の液体（含まれているポリマー類の構造もしくは組成物を劣化させることもなく、その中に吸収されもしない）とともに、耐爆性の容量３ガロンの商用グレードのワーナー(Warner)ブレンダー中で結合させる。含まれているハイドロゲルの構造体または組成物に吸収されない液体という場合、このような液体は、含まれているハイドロゲル形成吸収性ポリマー１グラムあたり液体約５グラム（重量で約５ｇ／ｇ）未満の少量範囲で構造体または組成物中に吸収されるにすぎないことを意味する。混合液を低速で約５分間攪拌する。混合液は、製紙ボックスの上方部分の底部に８０メッシュのナイロン成形用ワイヤー（ワイオミング州ニーナのプロダクティブ・ソルーション社(Productive Solutions, Inc.)のアップルトン(Appleton)製造事業部から入手可能）を備えた６インチ×６インチの「製紙ボックス(Paper Formation Box)」に注入される。液体レベルは、３Ａアルコール、または適切な溶液を加えて、スクリーンの約８インチ上方にする。液体排出の前に、パドルを使用して製紙ボックスの上部で溶液を完全に混合する。成形用ワイヤーの下方で弁を開き、液体を急速に排液し、成形用ワイヤー上への一様な堆積を確実にする。スクリーンを「製紙ボックス」から取り除き、ゆるく保持されている液体を除去するために真空源を横断して引き抜き、乾燥剤（たとえばミズーリ州６３１７８セントルイスのシグマ ケム社(Sigme Chem. Co.)のＤＲＩＥＲＩＴＥ）を含有するデシケーター中で一晩風乾させ、一様な水分量を保証する。いったん乾燥したら、吸収部材を成形用スクリーンから取り出す。
【０２１３】
毛管吸着吸収容量の測定のために、この部材から５．４ｃｍの円筒形構造体をアーチ・パンチする。この貯蔵吸収部材の毛管吸着等温線を図９にグラフで図示する。
【０２１４】
例２
ＨＩＰＥからの大表面積発泡体の調製
Ａ） ＨＩＰＥの調製
無水塩化カルシウム（３６．３２ｋｇ）と過硫酸カリウム（１８９ｇ）を３７８リットルの水中に溶解させる。これはＨＩＰＥエマルジョンを形成するための連続プロセスにおいて使用される水相の流れを提供する。
【０２１５】
蒸留ジビニルベンゼン（４２．４％ジビニルベンゼンおよび５７．６％エチルスチレン）（２６４０ｇ）、２−エチルヘキシルアクリレート（４４００ｇ）、およびヘキサンジオールジアクリレート（９６０ｇ）を含むモノマー混合物に、ジグリセロールモノオレエート乳化剤（４８０ｇ）、ジタロージメチルアンモニウムメチルスルフェート（８０ｇ）、およびチヌビン(Tinuvin)７６５（２０ｇ）を添加する。ジグリセロールモノオレエート乳化剤（グリンドステッド・プロダクツ(Grindsted Products)；ブラブランド(Brabrand)、デンマーク）は約８１％のジグリセロールモノオレエート、１％の他のジグリセロールモノエステル、３％のポリオール、および１５％のその他のポリグリセロールエステルを含み、約２．７ｄｙｎｅ／ｃｍの最小の油／水界面張力値を与え、約２．８重量％の油／水臨界凝集濃度を有する。混合後、この材料混合物を一晩静置させる。目に見える残留物は形成されず、混合物全部を取り出してＨＩＰＥエマルジョンを形成するための連続プロセスにおける油相として使用する。
【０２１６】
油相（２５℃）と水相（５３〜５５℃）の別個の流れがダイナミックミキシング装置へ供給される。ダイナミックミキシング装置中において結合された流れの完全な混合がピン・インペラによって達成される。ピン・インペラは長さ約３６．５ｃｍおよび直径約２．９ｃｍの円柱形のシャフトを有する。シャフトは６列のピンを保持しており、３列は３３個のピンおよび３列は３４個のピンを有し、各レベルの各々３個ずつのピンは互いに１２０°の角度に配置され、次の下方のレベルは隣接レベルに対して６０°で配置されて各レベルは０．０３ｍｍだけ離れており、各々のピンは０．５ｃｍの直径を有しシャフトの中心軸から２．３ｃｍの長さで外に向かって伸びている。ピン・インペラはダイナミックミキシング装置を形成する円筒形スリーブに取り付けられており、ピンは円筒形スリーブの壁から１．５ｍｍの間隔を有する。
【０２１７】
１９９６年９月１７日にＤｅｓＭａｒａｉｓによって出願された同時係属中の米国特許出願第０８／７１６，５１０号（その開示は参照により本明細書に組み込まれている）における図に示されているように、ダイナミックミキシング装置から出てくる排液の僅かな部分が回収され、再循環ゾーンに流入する。再循環ゾーンのワウケシャ(Waukesha)ポンプがこの僅かな部分をダイナミックミキシングゾーンへの油相および水相の流れの入口点へ戻す。
【０２１８】
スタティックミキサー（ＴＡＨインダストリーズ モデル１００−８１２）は外径１インチ（２．５ｃｍ）の１２のエレメントを有する。硬化のために使用される装置へのエマルジョンの供給を容易にするためにスタティックミキサーから下流にホースが取り付けられている。オプションで、ホースが充填され続けるように追加の逆圧を与えるために追加のスタティックミキサーを使用する。オプションのスタティックミキサーは１インチ（２．５ｃｍ）パイプ、１２エレメントのミキサー（マクマスター−キャル(McMaster-Carr)、オーロラ、オハイオ州、モデル３５２９Ｋ５３）でもよい。
【０２１９】
結合型混合再循環装置機構に水４部対油１部の比率で油相および水相を充填する。ダイナミックミキシング装置は、装置を完全に充填している間に空気を逃がすように排気される。充填中の流量は油相では７．５７ｇ／ｓｅｃおよび水相では３０．３ｃｃ／ｓｅｃである。
【０２２０】
装置機構を充填したら、インペラを１７５０ＲＰＭで回転させてダイナミックミキサーで攪拌を開始し、約３０ｃｃ／ｓｅｃの速度で再循環を開始する。その後、水相の流量は約１分間をかけて１５１．３ｃｃ／ｓｅｃへ徐々に増加させ、油相の流量は約３分間をかけて３．０３ｇ／ｓｅｃへ低下させる。再循環速度は後者の時間中に約１５０ｃｃ／ｓｅｃへ徐々に増加させる。この時点でダイナミックゾーンおよびスタティックミキサーによって作り出される逆圧は約１９．９ＰＳＩ（１３７ｋＰａ）であり、これはこのシステムのトータルの圧力降下を表す。その後、ワウケシャ(Waukesha)ポンプ（モデル３０）の速度を徐々に低下させ、約７５ｃｃ／ｓｅｃの再循環速度を生じさせる。
【０２２１】
Ｂ） ＨＩＰＥの重合
この時点でのスタティックミキサーからのＨＩＰＥの流れは、ケーキ作りに使用するスプリングフォーム・パンによく似た、取外し可能な側面を有する、直径４０インチ（１０２ｃｍ）および高さ１２．５インチ（３１．８ｃｍ）の円形ポリエチレン製タブに収集される。底部での直径が１２．５インチ（３１．８ｃｍ）のパイプ状ポリエチレン製インサートは底面の中心にしっかりと固定されており、高さは１２．５インチ（３１．８ｃｍ）である。ＨＩＰＥ含有タブは、６５℃に維持された室内で１８時間に渡って維持され、重合を実施して発泡体を形成する。
【０２２２】
Ｃ）発泡体の洗浄および水分除去
硬化したＨＩＰＥ発泡体は硬化用タブから取り出される。この時点での発泡体は重合したモノマーの重量の約４８〜５２倍（４８〜５２×）の残留水相（溶解した乳化剤、電解質、開始剤残留物および開始剤を含む）を有する。発泡体は鋭利な往復ソーブレードにより厚さ０．１８５インチ（４．７ｍｍ）のシートにスライスされる。その後、これらのシートは、発泡体の残留水相含量を徐々に低下させる真空を装備した一連の２個の多孔質ニップロールにより、重合材料の重量の約６倍（６×）にまで圧縮を受ける。この時点で、シートはさらに６０℃で１．５％ＣａＣｌ₂溶液により再飽和され、真空を装備した一連の３個の多孔質ニップロールにより、約４倍の水相含量にまで圧搾される。発泡体のＣａＣｌ₂含量は８〜１０％である。
【０２２３】
発泡体は最終ニップ後に厚さ約０．０２１インチ（０．０５３ｃｍ）に圧縮されたままになる。その後、発泡体は約１６時間風乾される。このような乾燥により、含水量を、重合材料の重量を単位として、約９〜１７％へ減少させる。この時点で、発泡体シートは極めてドレープ成形が可能で、「乾燥後の薄い状態（thin-after-drying）」である。
【０２２４】
例３
ＨＩＰＥからの大表面積発泡体の調製
Ａ） ＨＩＰＥの調製
ＨＩＰＥエマルジョンを形成するための連続プロセスにおいて使用する水相および油相の流れは例１に従って調製する。油相（２５℃）と水相（５３〜５５℃）の別個の流れが例１に詳述したダイナミックミキシング装置へ供給される。
【０２２５】
装置機構が充填されたら、インペラを１７００ＲＰＭで回転させてダイナミックミキサーでの攪拌を開始させ、約３０ｃｃ／ｓｅｃの速度で再循環を開始させる。その後、水相の流量は約１分間をかけて１５１．３ｃｃ／ｓｅｃへ徐々に増加させ、油相の流量は約３分間をかけて３．３６ｇ／ｓｅｃへ低下させる。再循環速度は後者の時間中に約１５０ｃｃ／ｓｅｃへ徐々に増加させる。この時点でダイナミックゾーンおよびスタティックミキサーによって作り出される逆圧は約１９．７ＰＳＩ（１３６ｋＰａ）であり、これはこのシステムのトータルの圧力降下を表す。その後、ワウケシャ(Waukesha)ポンプの速度は徐々に低下させ、約７５ｃｃ／ｓｅｃの再循環速度を生じさせる。
【０２２６】
Ｂ） ＨＩＰＥの重合
この時点でスタティックミキサーから流れてくるＨＩＰＥは、例１で詳述したようにして収集され、ポリマー発泡体へ硬化させられる。
【０２２７】
Ｃ） 発泡体の洗浄および水分除去
硬化したＨＩＰＥ発泡体は硬化用タブから取り出される。この時点の発泡体は重合したモノマーの重量の約４３〜４７倍（４３〜４７×）の残留水相（溶解した乳化剤、電解質、開始剤残留物および開始剤を含む）を有する。発泡体は鋭利な往復ソーブレードにより厚さ０．１８５インチ（４．７ｍｍ）のシートにスライスされる。その後、これらのシートは、発泡体の残留水相含量を徐々に低下させる真空を装備した一連の２個の多孔質ニップロールにより、重合材料の重量の約６倍（６×）にまで圧縮を受ける。この時点で、シートはさらに６０℃で１．５％のＣａＣｌ₂溶液により再飽和され、真空を装備した一連の３個の多孔質ニップロールにより、約４倍の水相含量にまで圧搾される。発泡体のＣａＣｌ₂含量は８〜１０％である。
【０２２８】
発泡体は最終ニップ後に厚さ約０．０２８インチ（０．０７１ｃｍ）に圧縮されたままになる。その後、発泡体は約１６時間風乾される。このような乾燥により、含水量を、重合材料の重量を単位として、約９〜１７％へ減少させる。この時点で、発泡体シートは極めてドレープ成形が可能で、「乾燥後の薄い状態(thin-after-drying)」である。
【０２２９】
例４
ＨＩＰＥからの大表面積発泡体の調製
Ａ） ＨＩＰＥの調製
ＨＩＰＥエマルジョンを形成するための連続プロセスにおいて使用する水相および油相の流れは例１に従って調製する。油相（２５℃）と水相（５３〜５５℃）の別個の流れが例１に詳述したダイナミックミキシング装置へ供給される。
【０２３０】
装置機構が充填されたら、インペラを１７５０ＲＰＭで回転させてダイナミックミキサーでの攪拌を開始させ、約３０ｃｃ／ｓｅｃの速度で再循環を開始させる。その後、水相の流量は約１分間をかけて１５１．３ｃｃ／ｓｅｃへ徐々に増加させ、さらに油相の流量は約３分間をかけて３．７８ｇ／ｓｅｃへ低下させる。再循環速度は後者の時間中に約１５０ｃｃ／ｓｅｃへ徐々に増加させる。この時点で、ダイナミックゾーンおよびスタティックミキサーによって作り出される逆圧は約１８．７ＰＳＩ（１２９ｋＰａ）であり、これはこのシステムのトータルの圧力降下を表す。その後、ワウケシャ(Waukesha)ポンプの速度は徐々に低下させ、約７５ｃｃ／ｓｅｃの再循環速度を生じさせる。
【０２３１】
Ｂ） ＨＩＰＥの重合
この時点でスタティックミキサーから流れてくるＨＩＰＥは、例１に詳述したようにして収集され、ポリマー発泡体へと硬化される。
【０２３２】
Ｃ） 発泡体の洗浄と水分除去
硬化したＨＩＰＥ発泡体は硬化用タブから取り出される。この時点での発泡体は、重合したモノマーの重量の約３８〜４２倍（３８〜４２×）の残留水相（溶解した乳化剤、電解質、開始剤残留物および開始剤を含む）を有する。発泡体は鋭利な往復ソーブレードにより厚さ０．１８５インチ（４．７ｍｍ）のシートにスライスされる。その後、これらのシートは、発泡体の残留水相含量を徐々に低下させる真空を装備した一連の２個の多孔質ニップロールにより、重合材料の重量の約６倍（６×）にまで圧縮を受ける。この時点で、シートはさらに６０℃で１．５％ＣａＣｌ₂溶液をにより再飽和され、真空を装備した一連の３個の多孔質ニップロールにより、約４倍の水相含量にまで圧搾される。発泡体のＣａＣｌ₂含量は８〜１０％である。
【０２３３】
発泡体は最終ニップ後に厚さ約０．０２８インチ（０．０７１ｃｍ）に圧縮されたままになる。その後、発泡体は約１６時間風乾される。このような乾燥により、含水量を、重合材料の重量を単位として、約９〜１７％へ減少させる。この時点で、発泡体シートは極めてドレープ成形が可能で、「乾燥後の薄い状態(thin-after-drying)」である。
【０２３４】
例５
大表面積ポリマー発泡体材料を含む貯蔵吸収部材
この例では、ヒドロゲル形成吸収性ポリマーおよび例３に従って調製された高い吸引性のポリマー発泡体を含む高い毛管吸引性の吸収部材について説明する。吸収性ポリマーおよびポリマー発泡体の分布が比較的均質に近いヒドロゲル形成吸収性ポリマーを含有する部材を構成するために、下記の手順に従う。
【０２３５】
１０ｇの風乾ポリマー発泡体（上記の例３に従って調製された）を、１リットルの２％塩化カルシウム溶液が入れられている１．２５リットルのジャーを備えたブレンダー（オスタライザー(Osterizer)モデル８４８−３６Ｌ）に入れる。発泡体材料の全てが確実に浸されるようにした後に、ブレンダーを「液化」（高設定）で１０秒間攪拌し、その後さらに「すりつぶし(Grate)」設定で５秒間攪拌する。その後、得られたスラリーをペーパー・タオルで裏張りしたブフナー漏斗（クアーズ(Coors)ＵＳＡモデル６０２８３）に移す。約５００ｍＬの液体が試料からフリーに排液される。その後、試料をゴムメンブレンで被覆し、真空（約５００ｍｍＨｇ）にかけて、５０〜６０ｇの重量にまで試料から水を取り除く。
【０２３６】
試料を乾燥したブレンダーのジャーへ戻し、試料をほぼ独立した粒子へ分散させるようにジャーおよびベースを数回逆転させ直立に戻しながら、「液化」に設定された攪拌により分散させる。その後、分散された試料を周囲条件下で風乾させた後、発泡体粒子をヒドロゲル形成吸収性ポリマー（ＡＳＡＰ２３００、イリノイ州パランティンのケムダルコーポレーション(Chemdal Corporation)から入手可能；また、オハイオ州シンシナティのザ・プロクター＆ギャンブル社(The Procter & Gamble CO.)の紙テクノロジー事業部からも入手可能）と結合させ、重量で５０％のヒドロゲル形成ポリマーおよび重量で５０％の大表面積ポリマー発泡体の均質混合物からなる貯蔵吸収部材を与える。
【０２３７】
この貯蔵吸収部材の毛管吸着等温線を図９にグラフで図示する。
【０２３８】
例６ 大表面積フィブレッツを含む貯蔵吸収部材
本例ではヒドロゲル形成吸収性ポリマーおよび大表面積フィブレッツを含む高い毛管吸引性の吸収部材について説明する。セルロースアセテートフィブレッツFibrets（登録商標）としてヘキストセラネーゼ社（Hoechst Celanese Cop.；シャルロット、ノースカロライナ州）から入手できる大表面積フィブレッツを、ヒドロゲル形成吸収性ポリマー（ＡＳＡＰ２３００、イリノイ州パランティンのケムダルコーポレーション(Chemdal Corporation)から入手可能；また、オハイオ州シンシナティのザ・プロクター＆ギャンブル社(The Procter & Gamble CO.)の紙テクノロジー事業部からも入手可能）と結合させて、重量で５０％のヒドロゲル形成ポリマーおよび重量で５０％のフィブレッツの均質混合物からなる貯蔵吸収部材を与える。
【０２３９】
この貯蔵吸収部材の毛管吸着等温線を図９にグラフで図示する。
【０２４０】
例７
大表面積ポリマー発泡体材料を含む貯蔵吸収部材
この例では、ヒドロゲル形成吸収性ポリマーおよび例３に従って調製された高い吸引性のポリマー発泡体を含む高い毛管吸引性の吸収部材について説明する。吸収性ポリマーおよびポリマー発泡体の分布が比較的均質に近いヒドロゲル形成吸収性ポリマーを含有する部材を構成するために、下記の手順に従う。
【０２４１】
１０ｇの風乾ポリマー発泡体（上記の例３に従って調製された）を、１リットルの２％塩化カルシウム溶液が入れられている１．２５リットルのジャーを備えたブレンダー（オスタライザー(Osterizer)モデル８４８−３６Ｌ）に入れる。発泡体材料の全てが確実に浸されるようにした後に、ブレンダーを「液化」（高設定）で１０秒間攪拌し、その後さらに「すりつぶし(Grate)」設定で５秒間攪拌する。その後、得られたスラリーをペーパー・タオルで裏張りしたブフナー漏斗（クアーズ(Coors)ＵＳＡモデル６０２８３）に移す。約５００ｍＬの液体が試料からフリーに排液される。その後、試料をゴムメンブレンで被覆し、真空（約５００ｍｍＨｇ）にかけて、５０〜６０ｇの重量にまで試料から水を取り除く。
【０２４２】
試料を乾燥したブレンダーのジャーへ戻し、試料をほぼ独立した粒子へ分散させるようにジャーおよびベースを数回逆転させ直立に戻しながら、「液化」に設定された攪拌により分散させる。その後、分散された試料を周囲条件下で風乾させた後、発泡体粒子を混合床イオン交換ヒドロゲル形成吸収性ポリマー（下記に記載されている）と結合させ、重量で６０％のヒドロゲル形成ポリマーおよび重量で４０％の大表面積ポリマー発泡体の均質混合物からなる貯蔵吸収部材を与える。
【０２４３】
Ａ） 混合床イオン交換吸収性ポリマーの調製
（ｉ） カチオン交換吸収性ポリマー−架橋ポリアクリル酸の調製
４５０グラムのアクリル酸モノマー（アルドリッチ・ケミカル社、カタログ番号１４，７２３−０、ロット番号１５９３０ＣＳ）を清浄な４０００ｍＬの樹脂ケトルに入れることにより、均質な架橋ポリアクリル酸を合成する。７．２グラムのＮ，Ｎ’−メチレンビスアクリルアミド（アルドリッチ・ケミカル社、カタログ番号１４，６０７−２、ロット番号０４５１１ＤＲ）および０．８５グラムの２，２’−アゾビス（２−アミジノプロパン）ジヒドロクロリド（和光、ロット番号Ｐ２１９７）を、２０５０グラムの水に溶解し、樹脂ケトル中のアクリル酸モノマーに加える。この溶液を窒素で１５分間スパージして溶解酸素を除去する。その後、樹脂ケトルをシールし、溶液を４０℃で１６時間加熱する。
【０２４４】
得られたゲルを冷却させた後、砕いて約１ｃｍ径の破片にし、真空オーブン中５５℃で６０時間乾燥する。ウィリーミルを用い、この試料を粉砕しＵＳＡ２０メッシュのふるいを通してふるい分けして、均一に架橋したポリアクリル酸を得る。
【０２４５】
（ii） アニオン交換吸収性ポリマー−架橋ポリアリルアミンの調製
ポリアリルアミン、１２５０グラムの２０％溶液（日東紡績社、東京、日本、ロット番号８０７２８）を２０００ｍＬのガラスジャーに秤量する。エチレングリコールエーテル、１９グラムの５０％溶液（アルドリッチ・ケミカル社、カタログ番号Ｅ２，７２０−３）を２０グラムの蒸留水で希釈し、ポリアリルアミン溶液に加える。混合物を、排気されているオーブン中に約６０℃で１昼夜入れるのに先立って、室温で約２分間攪拌する。
【０２４６】
得られたゲルを砕いて約５ｍｍ径の破片にし、高真空中で約９６時間乾燥して、軽く架橋したポリアリルアミンのアニオン交換吸収性ポリマーを得て、これを乾燥雰囲気下で保管する。
【０２４７】
（iii） 混合床イオン交換吸収性ポリマー
架橋ポリアリルアミンのアニオン交換吸収性ポリマーを粉砕し、ふるい分けする。ＵＳＡシリーズ標準２５メッシュふるいを通過するが、ＵＳＡシリーズ標準７０メッシュふるいを通過しない粒子サイズ部分（すなわち約２００〜７００ミクロン径の範囲にある粒子を含む部分）を収集する。
【０２４８】
約１２５グラムのふるい分けした架橋ポリアクリル酸（２００〜７００ミクロン径）のカチオン交換吸収性ポリマーと約１２５グラムのふるい分けした架橋ポリアリルアミンのアニオン交換吸収性ポリマーをいっしょに混合し、各タイプのポリマーの粒子が混合物全体にわたって均一に分布するようにした。この混合物は、この例の貯蔵吸収部材に用いられる混合床イオン交換吸収性ポリマー組成物を構成する。このような組成物に関するさらなる情報は、米国特許出願第 号（１９９９年３月１日出願、Ｈｉｒｄら）（Ｐ＆Ｇケース７４３２−名称「加圧下において高い吸着容量を有する吸収性ポリマー組成物」）に開示されており、これはすでに参照により本明細書に組み込まれている。
【０２４９】
この貯蔵吸収部材の毛管吸着等温線を図９にグラフで図示する。
【図面の簡単な説明】
【図１】 本発明の高い毛管吸引容量の貯蔵吸収部材を含む吸収性コアを有するおむつを分解して示す図。
【図２ａ】 図１に示されるようなおむつに含まれる代表的な多層コアを分解して示す図。
【図２ｂ】 図１に示されるようなおむつに含まれる他の代表的な多層コアを分解して示す図。
【図３】 本発明の貯蔵吸収部材に有用な、代表的な大表面積ポリマー発泡体の顕微鏡写真（倍率５００×）。
【図４】 図３に示された大表面積ポリマー発泡体の顕微鏡写真（ただし、倍率１０００×）。
【図５】 粒子状ヒドロゲル形成吸収性ポリマーおよび粒子状ポリマー吸収発泡体を含む本発明の貯蔵吸収部材の顕微鏡写真。
【図６】 粒子状ヒドロゲル形成吸収性ポリマーおよび大表面積セルロースアセテート繊維を含む本発明の貯蔵吸収部材の顕微鏡写真。
【図７】 粒子状ヒドロゲル形成吸収性ポリマーおよび大表面積ガラス超極細繊維を含む本発明の貯蔵吸収部材の顕微鏡写真。
【図８Ａ】 吸収部材の毛管吸着吸収容量を測定する装置の構成を示す図。
【図８Ｂ】 図８Ａに一般的に示されているガラスフリットを示す断面拡大図。
【図８Ｃ】 図８Ｂに示されているガラスフリットのシリンダー／ピストンアセンブリーを示す断面拡大図。
【図８Ｄ】 図８Ｃに示されているシリンダー／ピストンアセンブリーのピストンの外観を示す断面拡大図。
【図９】 本発明の種々の貯蔵吸収部材ならびにセルロース繊維（綿毛）およびヒドロゲル形成吸収性ポリマーを含む従来の部材（比較例Ａとして示される）について、毛管吸着等温線を示す図。
【図１０】 本発明の代表的な貯蔵吸収部材（この部材は粒子状ポリマー発泡体および粒子状ヒドロゲル形成吸収性ポリマーを含む）を形成するための装置の構成図。
【図１１】 本発明の代表的な貯蔵吸収部材を形成するための他の装置の構成図。
【図１２】 図１１に図示された装置を用いて製造された貯蔵吸収部材の斜視図。
【図１３】 図１２の一部を拡大して示す斜視図。[0001]
BACKGROUND OF THE INVENTION
The present application relates to absorbent members for body fluids such as urine and menstruation. The present application relates to an absorbent member having a particularly high capillary suction, which member comprises an osmotic absorbent, for example a hydrogel-forming absorbent polymer.
[0002]
[Prior art]
The development of highly absorbent components used in disposable diapers, adult incontinence pads and briefs, menstrual products such as sanitary napkins is an important commercial subject of interest. A highly desirable property for these products is thinness. For example, thinner diapers are not bulky to wear, fit well with underwear, and are less noticeable. They are also more compact in packaging, making it easier for consumers to transport and store diapers. In addition, the compactness when packaged includes a small shelf area per diaper unit required in the store for manufacturers and distributors, resulting in a reduction in distribution costs.
[0003]
The ability to provide thinner absorbent products, such as diapers, is contingent on the ability to develop relatively thin absorbent cores or structures that can capture and store large amounts of excretory fluids, particularly urine. In this regard, the use of certain absorbent polymers, often referred to as “hydrogels”, “superabsorbents” or “hydrocolloid” materials, has become particularly important. For example, U.S. Pat. No. 3,699,103 issued Jun. 13, 1972, which discloses the use of such absorbent polymers (hereinafter "hydrogel-forming absorbent polymers") in absorbent products. Harper et al.) And U.S. Pat. No. 3,770,731 (Harmon), issued June 20, 1972. In fact, the development of thinner diapers typically involves the ability of these thinner absorbent cores to take advantage of the ability of these hydrogel-forming absorbent polymers to absorb large amounts of waste fluid when used in combination with a fibrous matrix. It is a direct result. For example, U.S. Pat. No. 16, issued June 16, 1987, discloses a bilayer core structure comprising a fibrous matrix and a hydrogel-forming absorbent polymer useful in making thin, compact and bulky diapers. See US Pat. No. 4,673,402 (Weisman et al.) And US Pat. No. 4,935,022 (Lash et al.) Issued June 19, 1990. Also, U.S. Pat. No. 5,562,646 (Goldman et al.) Issued Oct. 8, 1996 and U.S. Pat. No. 5,599,335 issued Feb. 4, 1997 ( See also Goldman et al.). Both relate to an absorbent core comprising a region of high concentration of hydrogel-forming polymer that forms a continuous fluid transport zone through the gel as the polymer swells.
[0004]
In addition to hydrogel-forming absorbent polymers as a key element in absorbent product storage structures, the use of polymer foam materials derived from high internal phase water / oil emulsions ("HIPE") is equated. For example, US Pat. No. 5,260,345 issued on Nov. 9, 1993 (Desmarais et al.), US Pat. No. 5,387,207 issued Feb. 7, 1995 (Dyer). (Dyer et al.) And U.S. Pat. No. 5,560,222 (Desmarez et al.), Issued July 22, 1997. Foam materials, particularly those designed to function as liquid storage / redistribution elements, have better wicking and liquid distribution properties than storage structures comprising hydrogel-forming absorbent polymers in a fibrous matrix, It offers several advantages, including high storage capacity under pressure, flexibility, etc.
[0005]
The main focus of previous work in both the hydrogel-forming absorbent polymer and HIPE foam areas is the maximization of liquid storage capacity in relatively thin materials. The hydrogel-forming absorbent polymer material absorbs liquid and provides anti-spilling and drying of the absorbent product. Once absorbed, the liquid in the absorbent polymer is firmly held by osmotic pressure, which prevents the topsheet from getting wet again by previously absorbed urine. However, if the liquid does not reach its surface, the hydrogel-forming absorbent polymer itself has little ability to absorb the liquid. This is particularly important at high capillary heights (liquid is present only in small capillaries). For example, normal softwood pulp shows little uptake at a capillary suction height of 100 cm. For this reason, it is not surprising that the mixture of pulp and hydrogel-forming absorbent polymer shows little uptake at 100 cm. Thus, despite the progress made to achieve the goal of high liquid storage capacity with thin materials, there is a continuing need to provide high storage capacity materials that also exhibit high capillary attraction. Storage materials that exhibit high capillary suction capacity allow water to be removed from other absorbent cores, such as capture and distribution materials (typically one or both of which are contained in the absorbent core of the absorbent product) Will be. By completely removing water from these other absorbent core elements, these materials will allow for better handling of further liquid attacks by the wearer. In addition to the typical high capillary suction capacity, a particularly desirable property is the ability to provide such capacity at relatively high capillary suction heights. When the product is wet with liquid, the movement of the liquid from the discharge area (ie, the product crotch) to the front or back of the product can provide good wearer comfort. As will be apparent, the ability of storage materials to remove water from other core elements, especially the dispensing material that draws liquids to high capillary heights, is particularly related to their function as absorbent material in absorbent products. Yes.
[0006]
[Problems to be solved by the invention]
Accordingly, it is desirable to be able to provide a storage absorbent member having a high capillary suction capacity, which comprises a hydrogel-forming absorbent polymer or other material that absorbs liquid primarily as a result of osmotic pressure.
[0007]
[Means for Solving the Problems]
The present invention relates to an absorbent member useful for confinement (eg, storage) of body fluids such as urine. These storage and absorbent members comprise at least an osmotic absorbent material (eg, a hydrogel-forming absorbent polymer) and have a high capillary suction capacity. For purposes of disclosing the present invention, the capillary suction capacity is measured based on the ability of the member to take up liquid at the relatively high capillary pressure typically encountered when the member is placed in an absorbent product. In particular, the capillary suction capacity is measured based on the capillary absorption capacity of the member, and the capillary absorption capacity is measured according to the capillary adsorption method described in the test method section below.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
I. Definition
As used herein, the term “body fluid” includes but is not limited to urine, menstruation, vaginal discharge, sweat and feces.
[0009]
As used herein, the term “absorbent core” refers to the element of an absorbent product that plays a major role in the liquid handling properties of the product (including body fluid capture, transport, distribution and storage). Say. For this reason, absorbent cores typically do not include a topsheet or backsheet of absorbent product.
[0010]
As used herein, the term “absorbent member” typically refers to an element of an absorbent core that provides one or more liquid handling properties such as liquid capture, liquid distribution, liquid transport, liquid storage, etc. That means. The absorbent member may constitute the entire absorbent core or part of the absorbent core, i.e. the absorbent core may comprise one or more absorbent members. A “storage absorbent member” is an absorbent member element of an absorbent core that functions to store primarily absorbed liquid. As described above, the storage absorbent member can also function to dispense liquid as a result of its vertical wicking capability.
[0011]
As used herein, the term “layer” refers to an absorbent member whose major dimensions are XY, ie along its length and width. It should be understood that the term layer is not necessarily limited to a single layer or sheet of material. The layer may then consist of a laminate or combination of several sheets or webs of the required type of material. Thus, the term “layer” includes the terms “layers” and “layered”.
[0012]
As used herein, the term “osmotic absorbent” refers to a material or structure that absorbs a solution depending on the chemical potential difference between the absorbed and unabsorbed solution. In general, this chemical potential difference results from the high solute concentration of the absorbed solution. In order to inhibit solute concentration homogenization due to diffusion of solute species, osmotic absorbents typically have a diffusion barrier that selectively inhibits diffusion of at least one solute species. Suitable diffusion barriers include (i) a semi-permeable reverse osmosis membrane (the membrane provides a diffusion barrier for soluble salts (eg, NaCl)), (ii) a crosslinked polyelectrolyte network (eg, used in hydrogels) (poly The electrolyte network retains counter ions dissociated inside the gel as a result of electrical neutralization considerations). Osmotic packet or chamber absorbents are described in US Pat. No. 5,108,383 (issued April 28, 1992 to White) and US Pat. No. 5,082,723 (January 21, 1992). Issued to Gross et al., Each of which is incorporated herein by reference. A particularly preferred osmotic absorbent for use in the storage absorbent member of the present invention is a hydrogel-forming absorbent polymer described in detail below.
[0013]
As used herein, the term “XY dimension” refers to a plane perpendicular to the thickness of a member, core or product. The XY dimensions typically correspond to the length and width of the member, core or product, respectively.
[0014]
As used herein, the term “region” or “zone” refers to a portion or section of an absorbent member.
[0015]
As used herein, the term “Z dimension” refers to a dimension orthogonal to the length and width of a member, core or product. The Z dimension usually corresponds to the thickness of the member, core or product.
[0016]
Also, for purposes of the present invention, the term “above” refers to an absorbent member, such as a layer, that is closest to the wearer of the absorbent product and typically relatively close to the topsheet of the absorbent product. Should be understood. Conversely, the term “downward” refers to an absorbent member that is furthest away from the wearer of the absorbent product and is typically closer to the backsheet.
[0017]
As used herein, the term “comprising” means that various elements, members, processes, etc., are used jointly in accordance with the present invention. Thus, the term “comprising” includes the more restrictive terms “consisting essentially of” and “consisting of”, the latter more restrictive term being Has a standard meaning as understood in this field.
[0018]
All percentages, ratios and proportions used herein are by weight unless otherwise specified.
[0019]
II. Capillary adsorption characteristics of storage absorbent members
The storage absorbent member of the present invention exhibits a high capillary suction capacity. For purposes of the present disclosure, this high suction capacity is measured based on the ability of the member to take up liquid at high capillary heights, typically encountered when the member is placed in an absorbent product. The capillary adsorption capacity test (also referred to herein as the capillary adsorption test) measures the amount of test liquid per gram of storage absorbent member that is taken up when the storage member is placed at various heights in the capillary adsorption device. taking measurement. The capillary adsorption capacity test is described in more detail in the test method section below. A capillary adsorption isotherm of a typical storage absorbent member is shown graphically in FIG. In particular, the capillary adsorption isotherm is shown below. (I) a storage absorbent member comprising high surface area glass ultrafine fibers and hydrogel-forming absorbent polymer particles (manufactured according to Example 1 below); (ii) high surface area polymer foam particles and hydrogel-forming absorbent. A storage absorbent member comprising polymer particles (produced according to Example 5 below); (iii) a storage absorbent member comprising large surface area cellulose acetate fibrets and hydrogel-forming absorbent polymer particles (according to Example 6 below) And (iv) a storage absorbent member (made according to Example 7 below) consisting of particles of high surface area polymer foam and particles of hydrogel-forming absorbent polymer. A capillary adsorption isotherm of a material representative of the prior art is also shown in FIG. Prior art samples consisted of about 42% cellulose fluff (Weint Hauser, Flint River Pulp, WA) and about 58% hydrogel-forming absorbent polymer (Clariant GmbH, IM7300 from Frankfurt). A 5.4 cm circular structure punched from a member made of (available below).
[0020]
In one embodiment, the high capillary suction storage absorbent member of the present invention comprises an osmotic absorbent (preferably a hydrogel-forming absorbent material) and is at least about 12 g / g, preferably at least about 35 cm high. It has a capillary adsorption capacity of 14 g / g, more preferably at least about 16 g / g, more preferably at least about 20 g / g, more preferably at least about 22 g / g, even more preferably at least about 35 g / g. Typically, these storage absorbent members are about 12 g / g to about 60 g / g or no more than about 70 g / g, more typically about 14 g / g to about 50 g / g or 35 cm high. At most about 60 g / g, more typically from about 16 g / g to about 40 g / g or at most about 55 g / g, more typically from about 20 g / g to about 50 g / g, more typically about It will have a capillary adsorption capacity of 22 g / g to about 45 g / g.
[0021]
In other embodiments, the high capillary suction storage absorbent member comprises an osmotic absorbent (preferably a hydrogel-forming absorbent material) and is at least about 7 g / g, preferably at least about 9 g / g at a height of 50 cm. More preferably at least about 12 g / g, even more preferably at least about 16 g / g, even more preferably at least about 21 g / g, even more preferably at least about 30 g / g. Typically, these storage absorbent members are about 7 g / g to about 40 g / g or at most about 60 g / g, more typically about 9 g / g to about 35 g / g or 50 cm in height. At most about 50 g / g, even more typically from about 12 g / g to about 30 g / g or at most about 45 g / g, even more typically from about 16 g / g to about 40 g / g, more typically Will have a capillary adsorption capacity of about 21 g / g to about 35 g / g.
[0022]
In yet another aspect, the high capillary suction storage absorbent member comprises an osmotic absorbent (preferably a hydrogel-forming absorbent material) and is at least about 4 g / g, preferably at least about 6 g / g at a height of 100 cm. g, more preferably at least about 8 g / g, even more preferably at least about 12 g / g, even more preferably at least about 17 g / g, even more preferably at least about 25 g / g. Typically, these storage absorbent members are from about 4 g / g to about 30 g / g or at most about 50 g / g, more typically from about 6 g / g to about 25 g / g or 100 cm high. At most about 45 g / g, even more typically from about 8 g / g to about 20 g / g or at most about 40 g / g, even more typically from about 12 g / g to about 35 g / g, even more typical Will have a capillary adsorption capacity of about 17 g / g to about 30 g / g.
[0023]
In yet another aspect, the high capillary suction storage absorbent member comprises an osmotic absorbent (preferably a hydrogel-forming absorbent material) and is at least about 4 g / g, preferably at least about 5 g / g at a height of 140 cm. g, more preferably at least about 7 g / g, even more preferably at least about 10 g / g, even more preferably at least about 14 g / g, even more preferably at least about 23 g / g. Typically, these storage absorbent members are at a height of 140 cm, from about 4 g / g to about 28 g / g or at most about 45 g / g, more typically from about 5 g / g to about 23 g / g or At most about 40 g / g, even more typically from about 7 g / g to about 18 g / g or at most about 35 g / g, even more typically from about 10 g / g to about 30 g / g, even more typical Will have a capillary adsorption capacity of about 14 g / g to about 25 g / g.
[0024]
In yet another aspect, the high capillary suction storage absorbent member comprises an osmotic absorbent (preferably a hydrogel-forming absorbent material) and is at least about 3 g / g, preferably at least about 4 g / g at a height of 200 cm. g, more preferably at least about 6 g / g, even more preferably at least about 8 g / g, even more preferably at least about 11 g / g, even more preferably at least about 20 g / g. Typically, these storage absorbent members are about 3 g / g to about 25 g / g or no more than about 40 g / g, more typically about 4 g / g to about 20 g / g or 200 cm high. At most about 35 g / g, even more typically from about 6 g / g to about 15 g / g or at most about 30 g / g, even more typically from about 8 g / g to about 25 g / g, even more typical Will have a capillary adsorption capacity of about 11 g / g to about 23 g / g.
[0025]
In addition to or instead of defining the high capillary suction capacity of the members of the present invention based on the capillary absorption capacity, particularly preferred members (eg, those where the high surface area material is a polymer foam) are of high height. It can also be characterized by its ability to take up liquid initially at a relatively fast rate. A high capillary suction member that exhibits both high uptake at high suction and high initial effective uptake rate is due to its high capillary suction material and the extent of partitioning from other absorbent core members (eg capture material or dispensing material) and its The speed should be improved conveniently and should give the user a good feeling of dryness. For purposes of this disclosure, the latter property is referred to herein as the “initial effective uptake rate at 200 cm capillary suction height” of the member (herein referred to as “initial effective uptake rate at 200 cm”). ), Reported in units of g / g / hour. The initial effective uptake rate of the storage absorbent member is calculated by dividing the capillary suction absorption capacity at 200 cm by the time spent at 200 cm. Capillary suction absorption capacity and time are readily determined by using the capillary adsorption method described in detail in the Test Methods section below. Although not required, a particularly preferred storage absorbent member is an initial at 200 cm of at least about 3 g / g / hr, more preferably at least about 4 g / g / hr, most preferably at least about 8 g / g / hr. Will have an effective uptake rate. Typically, the initial effective uptake rate at 200 cm is about 3 to about 15 g / g / hr, more typically about 4 to about 12 g / g / hr, and even more typically about 8 to about 12 g. / G / hr.
[0026]
The above-mentioned minimum capillary absorption capacity is important by the absorbent member of the present invention, but the member should have a capillary absorption capacity of at least 15 g / g at zero head pressure (ie at 0 cm in the capillary adsorption test). Not preferred). In other preferred embodiments, the absorbent member will exhibit the required g / g uptake together at at least two suction heights. Thus, for example, a preferred storage absorbent member will have two or more of the following characteristics: (I) at a height of 35 cm, at least about 12 g / g, preferably at least about 14 g / g, more preferably at least about 16 g / g, even more preferably at least about 20 g / g, even more preferably at least about 22 g / g g, even more preferably at least about 35 g / g capillary adsorption capacity; (ii) at a height of 50 cm, at least about 7 g / g, preferably at least about 9 g / g, more preferably at least about 12 g / g, further More preferably at least about 16 g / g, even more preferably at least about 21 g / g, even more preferably at least about 30 g / g capillary absorption capacity; (iii) at a height of 100 cm, at least about 4 g / g, preferably Is at least about 6 g / g, more preferably at least about 8 g / g, even more preferred Or at least about 12 g / g, even more preferably at least about 17 g / g, even more preferably at least about 25 g / g capillary absorption capacity; (iv) at a height of 140 cm, at least about 4 g / g, preferably A capillary adsorption capacity of at least about 5 g / g, more preferably at least about 7 g / g, even more preferably at least about 10 g / g, even more preferably at least about 14 g / g, even more preferably at least about 23 g / g; (V) at a height of 200 cm, at least about 3 g / g, preferably at least about 4 g / g, more preferably at least about 6 g / g, even more preferably at least about 8 g / g, even more preferably at least about 11 g / g. g, even more preferably at least about 20 g / g capillary adsorption capacity.
[0027]
In yet another aspect, the storage absorbent member of the present invention exhibits relatively high absorption efficiency (hereinafter referred to as “capillary absorption efficiency”) relative to the capacity of the member at zero head pressure at various heights. Can be characterized based on The capillary absorption efficiency at a given suction height is determined by dividing the capillary suction absorption capacity of the member at that given height by the capillary suction absorption capacity of that material at zero head pressure. In this regard, in one aspect, the absorbent member has a zero height height of at least about 15 g / g, preferably at least about 20 g / g, more preferably at least about 40 g / g, more preferably at least about 60 g / g capillary adsorption. Have an absorption capacity and have a capillary absorption efficiency of at least about 25%, preferably at least about 40%, even more preferably at least about 60%, even more preferably at least about 70% at a height of 100 cm. Let's go. In other embodiments, the absorbent member has a capillary adsorption capacity at zero height of at least about 15 g / g, preferably at least about 20 g / g, more preferably at least about 40 g / g, more preferably at least about 60 g / g. And at a height of 50 cm will have a capillary absorption efficiency of at least 30%, preferably at least 50%, more preferably at least 70%, even more preferably at least about 80%. In yet another aspect, the absorbent member has a capillary adsorption capacity at zero height of at least about 15 g / g, preferably at least about 20 g / g, more preferably at least about 40 g / g, more preferably at least about 60 g / g. And at a height of 35 cm will have a capillary absorption efficiency of at least 50%, preferably at least 70%, more preferably at least 85%, even more preferably at least about 90%.
[0028]
In another aspect, the preferred storage absorbent member of the present invention is a relatively high intermediate absorbent height, defined as the height at which the member has a capillary absorbent capacity of 50% of the capillary absorbent capacity at 0 cm height. Would have. In this regard, in one aspect, the absorbent member has a zero height height of at least about 15 g / g, preferably at least about 20 g / g, more preferably at least about 40 g / g, more preferably at least about 60 g / g capillary adsorption. Has an absorption capacity and is at least about 35 cm, more preferably at least about 40 cm, even more preferably at least about 50 cm, even more preferably at least about 100 cm, even more preferably at least about 130 cm, even more preferably at least about 200 cm. It will have an intermediate absorption height.
[0029]
III. Highly absorbent storage element
As indicated above, the storage absorbent member of the present invention comprises an osmotic absorbent, such as a hydrogel-forming absorbent polymer, and a high surface area material that facilitates the transport of bodily fluids to the osmotic absorbent. Exemplary materials useful for preparing the storage absorbent member of the present invention are described in detail below. Although other osmotic absorbents may be used for the storage member, hydrogel-forming absorbent polymers are preferred. Therefore, these materials will be described in detail.
[0030]
A. Hydrogel-forming absorbent polymer
1. Chemical composition
The storage absorbent member of the present invention preferably has at least one hydrogel-forming absorbent polymer (also referred to as a hydrogel-forming polymer). Hydrogel-forming polymers useful in the present invention include water-swellable polymers that are insoluble in various waters but can absorb large amounts of liquid. Such hydrogel-forming polymers are well known in the art, and any of these materials are useful in the high capillary suction absorbent member of the present invention.
[0031]
Hydrogel-forming absorbent polymer materials, also commonly referred to as “hydrocolloid” or “superabsorbent” materials, are polysaccharides such as carboxymethyl starch, carboxymethylcellulose, and hydroxypropylcellulose; polyvinyl alcohol and polyvinyl ether Nonionic types such as: polyvinylvinylidene, polyvinylmorpholinion, and cationic types such as N, N-dimethylaminoethyl or N, N-diethylaminopropyl acrylate and methacrylate, and their respective quaternary salts Can be included. Typically, hydrogel-forming absorbent polymers useful in the present invention have a plurality of anionic functional groups such as sulfonic acids, and more typically carboxy groups. Examples of suitable polymers for use herein include those prepared from polymerizable unsaturated acid-containing monomers. Thus, such monomers include olefinic unsaturated acids and anhydrides containing at least one carbon-carbon olefinic double bond. More specifically, these monomers can be selected from olefinically unsaturated carboxylic acids and anhydrides, olefinically unsaturated sulfonic acids, and mixtures thereof. As noted above, the nature of the hydrogel-forming absorbent polymer is not critical to the members of the present invention. Nevertheless, the selection of the optimal polymer material may enhance the performance characteristics of the members of the present invention. The following describes the preferred properties of the absorbent polymer useful herein. These properties should not be construed as limiting. Rather, they simply represent the progress that has occurred in absorbent polymer technology over the last few years.
[0032]
Here, in the preparation of the hydrogel-forming absorbent polymer, a part of the non-acid monomer may be contained usually in a very small amount. Such non-acid monomers include, for example, water-soluble or water-dispersible esters of acid-containing monomers, and monomers that do not contain any carboxylic acid or sulfonic acid groups. Thus, optional non-acid monomers can contain monomers containing the following types of functional groups: carboxylic or sulfonate esters, hydroxyl groups, amide groups, amino groups, nitrile groups, quaternary ammonium bases. An aryl group (eg, a phenyl group such as that derived from a styrene monomer). These non-acid monomers are well known materials such as US Pat. No. 4,076,663 (Masuda et al.) Issued on Feb. 28, 1978, and U.S. Patent issued on Dec. 13, 1977. No. 4,062,817 (Westerman) is described in great detail, both of which are incorporated herein by reference.
[0033]
Olefinic unsaturated carboxylic acid and carboxylic anhydride monomers include acrylic acid itself, methacrylic acid, ethacrylic acid, α-chloroacrylic acid, a-cyanoacrylic acid, β-methylacrylic acid (crotonic acid), α-phenyl Acrylic acid, β-acryloxypropionic acid, sorbic acid, α-chlorosorbic acid, angelic acid, cinnamic acid, p-chlorocinnamic acid, β-sterylacrylic acid, itaconic acid, citroconic acid, mesaconic acid, glutaconic acid, Included are acrylic acids such as aconitic acid, maleic acid, fumaric acid, tricarboxyethylene and maleic anhydride.
[0034]
Examples of olefinic unsaturated sulfonic acid monomers include aliphatic or aromatic vinyl sulfonic acids such as vinyl sulfonic acid, allyl sulfonic acid, vinyl toluene sulfonic acid and styrene sulfonic acid; sulfoethyl acrylate, sulfoethyl methacrylate, sulfopropyl acrylate Acrylic and methacrylic sulfonic acids such as sulfopropyl methacrylate, 2-hydroxy-3-methacryloxypropyl sulfonic acid and 2-acrylamido-2-methylpropane sulfonic acid.
[0035]
Preferred hydrogel-forming absorbent polymers for use in the present invention contain carboxy groups. These polymers include hydrolyzed starch-acrylonitrile graft copolymer, partially neutralized hydrolyzed starch-acrylonitrile graft copolymer, starch-acrylic acid graft copolymer, partially neutralized starch. -Acrylic acid graft copolymer, saponified vinyl acetate-acrylic ester copolymer, hydrolyzed acrylonitrile or acrylamide copolymer, slightly network cross-linked polymer of any of the above copolymers, partially neutralized Polyacrylic acid and slightly network cross-linked polymers of partially neutralized polyacrylic acid are included. These polymers can be used either alone or in the form of a mixture of two or more different polymers. Examples of these polymeric materials are US Pat. No. 3,661,875, US Pat. No. 4,076,663, US Pat. No. 4,093,776, US Pat. No. 4,666,983, and US Pat. This is disclosed in Japanese Patent No. 4,734,478.
[0036]
The most preferred polymeric material used in the preparation of the hydrogel-forming absorbent polymer is a slightly network crosslinked polymer of partially neutralized polyacrylic acid and its starch derivative. Most preferably, the hydrogel-forming absorbent polymer comprises from about 50 to about 95%, preferably about 75% neutralized and slightly network cross-linked polyacrylic acid (ie poly (sodium acrylate / acrylic acid)). Network cross-linking renders the polymer substantially insoluble in water and, in part, determines the absorption capacity and extractable polymer content characteristics of the hydrogel-forming absorbent polymer. Processes for network crosslinking of these polymers and representative network crosslinkers are described in greater detail in US Pat. No. 4,076,663.
[0037]
The hydrogel-forming absorbent polymer is preferably one type (ie, homogeneous), although mixtures of polymers can be used in the present invention. For example, in the present invention, a mixture of a starch-acrylic acid graft copolymer and a slightly network crosslinked polymer of partially neutralized polyacrylic acid can be used.
[0038]
The hydrogel forming polymer component may be in the form of a mixed bed ion exchange composition comprising a cation exchange hydrogel forming absorbent polymer and an anion exchange hydrogel forming absorbent polymer. Such a mixed bed ion exchange composition is, for example, US patent application Ser. No. 09 / 003,565 filed Jan. 7, 1998 by Hird et al. (P & G Case 6975-name “having high adsorption capacity under pressure. ABSORBENT POLYMER COMPOSITIONS HAVING HIGH SORPTION CAPACITIES UNDER AN APPLIED PRESSURE); US patent application Ser. No. 09 / 003,905 filed Jan. 7, 1998 (P & G cases 6976 and 6976R). -Name “ABSORBENT POLYMER COMPOSITIONS WITH HIGH SORPTION CAPACITY AND HIGH FLUID PERMEABILITY UNDER AN APPLIED PRESSURE”); January 7, 1998 by Ashraf et al. US patent application Ser. No. 09 / 003,918 filed on the same day (P & G case 6977-name “under pressure” ABSORBENT POLYMER COMPOSITIONS WITH HIGH SORPTION CAPACITY UNDER AN APPLIED PRESSURE AND IMPROVED INTEGRITY IN THE SWOLLEN STATE) ”); and Hird et al., 1999, 3 US Patent Application No. (P & G Case 7432-Named “ABSORBENT POLYMER COMPOSITIONS HAVING HIGH SORPTION CAPACITIES UNDER AN APPLIED PRESSURE”) filed on Jan. 1 The disclosures of each of which are incorporated herein by reference.
[0039]
Hydrogel-forming absorbent polymers useful in the present invention can have a wide variety of sizes, shapes and / or morphologies. These polymers may be in the form of particles (eg, granules, powders, interparticle aggregates, interparticle cross-linked aggregates, etc.) that do not have a large ratio of maximum dimension to minimum dimension, and fibers, sheets, films, It may be in the form of a foam or flake. The hydrogel-forming absorbent polymer may consist of a mixture with low levels of one or more additives such as powdered silica, surfactants, glues, binders and the like. The components in the mixture may be physically and / or chemically associated in such a way that the hydrogel-forming polymer component and the non-hydrogel-forming polymer additive are not easily physically separable.
[0040]
The hydrogel-forming absorbent polymer may be essentially non-porous (ie without internal porosity) or may have substantial internal porosity.
[0041]
For particles as described above, particle size is defined as the dimension measured by sieve size analysis. Thus, for example, particles retained on a US standard test sieve having an aperture of 710 microns (eg, No. 25 US series alternative sieve display) are considered to have a size greater than 710 microns; Particles that pass through but are retained on a 500 micron sieve (eg No. 35 US series alternative sieve display) are considered to have a particle size between 500 and 710 μm; and a 500 micron sieve Particles passing through are considered to have a size of less than 500 μm. The mass median particle size of a given sample of hydrogel-forming absorbent polymer particles is defined as the particle size that divides the sample in half on a mass basis. That is, half of the sample by weight will have a particle size smaller than the mass median size and half of the sample will have a particle size larger than the mass median size. When the 50% mass value does not correspond to the opening size of a US standard test sieve, typically the standard particle size plot method (retained on an opening of a given sieve size is used to determine the mass median particle size. Or the cumulative weight percent of the particle sample passing through the aperture is plotted on the probability paper against the size of the sieve aperture). These methods for measuring the size of hydrogel-forming absorbent polymer particles are described in detail in US Pat. No. 5,061,259 (Goldman et al.), Issued Oct. 29, 1991, This is incorporated herein by reference.
[0042]
For hydrogel-forming absorbent polymer particles useful in the present invention, the particles will generally have a size in the range of about 1 to about 2,000 μm, more preferably about 20 to about 1,000 μm. The mass median particle size will generally be from about 20 to about 1,500 μm, more preferably from about 50 μm to about 1,000 μm, even more preferably from about 100 μm to about 800 μm.
[0043]
If relatively high concentrations of hydrogel-forming absorbent polymer are used in the absorbent member of the present invention (eg, 40-60% or more by weight), further properties of the absorbent polymer may be relevant. In such embodiments, the material is made from US Pat. No. 5,562,646 issued to Goldman et al. On Oct. 8, 1996, and US Pat. No. 5,562 issued to Goldman et al. On Feb. 4, 1997. May have one or more of the characteristics described by 599,335, the disclosure of each of which is incorporated herein by reference.
[0044]
2. Production method
The basic hydrogel-forming absorbent polymer can be formed by any conventional method. A typical and preferred process for making these polymers is described in US Reissue Patent No. 32,649 (Brandt et al.) Issued April 19, 1988, US issued May 19, 1987. No. 4,666,983 (Tsubakimoto et al.) And US Pat. No. 4,625,001 (Tsubakimoto et al.) Issued Nov. 25, 1986, all of which are incorporated herein by reference. Incorporated in the description.
[0045]
A preferred method for forming the basic hydrogel-forming absorbent polymer is a method comprising an aqueous solution or other solution polymerization method. As described in US Reissue Pat. No. 32,649 referenced above, the aqueous polymerization process involves the use of an aqueous reaction mixture to effect the polymerization. The aqueous reaction mixture is then subjected to polymerization conditions sufficient to produce a slightly network cross-linked polymer that is substantially insoluble in water in the mixture. The formed polymer mass is then crushed or cut to form individual particles.
[0046]
More specifically, an aqueous solution polymerization method for producing a hydrogel-forming absorbent polymer involves the preparation of an aqueous reaction mixture for performing polymerization therein. One element of such a reaction mixture is an acid group-containing monomer that will form the “backbone” of the hydrogel-forming absorbent polymer produced. The reaction mixture will generally contain about 100 parts by weight of monomer. Another component of the aqueous reaction mixture includes a network crosslinker. Network crosslinkers useful for forming hydrogel-forming absorbent polymers according to the present invention are the above-referenced US Reissue Patent No. 32,649, US Pat. No. 4,666,983 and US Pat. No. 4,625,001. Is described in more detail in the issue. The network crosslinker will generally be present in the aqueous reaction mixture in an amount from about 0.001 mole percent to about 5 mole percent, based on the total moles of monomer present in the aqueous mixture (100 parts by weight of monomer). From about 0.01 to about 20 parts by weight). Optional components of the aqueous reaction mixture include, for example, sodium, potassium and ammonium persulfates, caprylyl peroxide, benzoyl peroxide, hydrogen peroxide, cumene hydroperoxide, tertiary butyl diperphthalate, tertiary butyl perbenzoate, peroxide. It consists of a free radical initiator containing peroxygen compounds such as sodium acetate, sodium percarbonate and the like. Other optional components of the aqueous reaction mixture consist of a variety of non-acidic comonomers including esters of essential unsaturated acid functional group-containing monomers or other comonomers that do not contain any other carboxylic or sulfonic acid functional groups.
[0047]
The aqueous reaction mixture is subjected to polymerization conditions sufficient to produce a slightly network crosslinked polymer of the hydrogel-forming absorbent that is substantially insoluble in water but water swellable in the mixture. Polymerization conditions are also discussed in more detail in the above three patents. Such polymerization conditions generally include heating to a polymerization temperature of about 0 ° C. to about 100 ° C., more preferably about 5 ° C. to about 40 ° C. (thermal activation method). The polymerization conditions under which the aqueous reaction mixture is maintained may include, for example, subjecting the reaction mixture or portions thereof to any conventional polymerization activating radiation. Irradiation with radiation, electron beam, ultraviolet light or electromagnetic waves is an alternative conventional polymerization method.
[0048]
Also, the acidic functional groups of the hydrogel-forming absorbent polymer formed in the aqueous reaction mixture are preferably neutralized. Neutralization is any acid group-containing monomer that is neutralized with a salt-forming cation, which results in at least 25 mole percent, more preferably at least about 50 mole percent of all monomers utilized to form the polymer. The conventional method can be used. Such salt-forming cations include, for example, alkali metals, ammonium, substituted ammonium and amines as discussed in detail in US Reissue Pat. No. 32,649 referenced above.
[0049]
Although it is preferred to produce hydrogel-forming absorbent polymers in the form of microparticles using an aqueous solution polymerization process, the polymerization process is carried out using a multiphase polymerization process such as an inverse emulsion polymerization method or an inverse suspension polymerization method. You can also. In inverse emulsion polymerization or inverse suspension polymerization, an aqueous reaction mixture as described above is suspended in the form of small droplets in a matrix of an inert organic solvent that is immiscible in water, such as cyclohexane. The resulting hydrogel-forming absorbent polymer particles are generally spherical in shape. Inverse suspension polymerization methods are described in US Pat. No. 4,340,706 (Obayashi et al.) Issued July 20, 1982, US Pat. No. 4,506,052 issued March 19, 1985. (Flesher et al.), And U.S. Pat. No. 4,735,987 (Morita et al.) Issued April 5, 1988, all of which are incorporated herein by reference. .
[0050]
Surface cross-linking of the initially formed polymer may be beneficial in the context of the present invention, a relatively high porosity hydrogel layer ("PHL"), performance under pressure ("PUP") capacity and brine flow A preferred process for obtaining a hydrogel-forming absorbent polymer having a conductivity (“SFC”) value. A general method suitable for surface cross-linking of hydrogel-forming absorbent polymers according to the present invention is described in US Pat. No. 4,541,871 (Obayashi), issued September 17, 1985; October 1992. PCT Application No. WO92 / 16565 (Stanley) published on 1st; PCT Application No. WO90 / 08789 (Tai) published on 9th August 1990; PCT Application published on 18th March 1993 WO 93/05080 (Stanley); US Pat. No. 4,824,901 issued on April 25, 1989 (Alexander); US Pat. No. 4,789,861 issued on January 17, 1989 (Johnson); US Pat. No. 4,587,308 issued on May 6, 1986 (Makita); US Pat. No. 4,734,478 issued on March 29, 1988 (Tsuba) kimoto); U.S. Pat. No. 5,164,459 issued on November 17, 1992 (Kimura et al.); Published German Patent Application No. 4,020,780 published on August 29, 1991 (Dahmen) And published European Patent Application No. 509,708 (Gartner) published Oct. 21, 1992, all of which are incorporated herein by reference. See also US Pat. No. 5,562,646 issued on Oct. 8, 1996 (Goldmann et al.) And US Pat. No. 5,599,335 issued on Feb. 4, 1997 (Goldmann et al.). I want.
[0051]
Hydrogel-forming absorbent polymer particles prepared according to the present invention are typically substantially dry. The term “substantially dry” as used herein refers to a liquid content in which the particles are less than about 50%, preferably less than about 20%, more preferably less than about 10% by weight of the particles. , Typically means having a water or other solution content. Generally, the liquid content of the hydrogel-forming absorbent polymer particles is in the range of about 0.01% to about 5% by weight of the particles. Individual particles can be dried by any conventional method, such as by heating. Alternatively, if the particles are formed using an aqueous reaction mixture, water may be removed from the reaction mixture by azeotropic distillation. The polymer-containing aqueous reaction mixture can also be treated with a dehydrating solvent such as methanol. Combinations of these drying methods can also be used. The polymer mass from which the water has been removed may then be cut or ground to form substantially dry particles of the hydrogel-forming absorbent polymer.
[0052]
B. Large surface area material
In addition to the osmotic absorbent (eg, hydrogel-forming absorbent polymer), the storage absorbent member of the present invention includes a high surface area material. It is this high surface area material that, by itself or in combination with, for example, a hydrogel-forming absorbent polymer, gives the member a high capillary adsorption capacity. As far as discussed herein, in at least one aspect, large surface area materials can be absorbed into their capillary adsorption capacity (hydrogel-forming polymers or other optional materials included in the actual storage absorbent member, such as adhesives, (Measured without including a binder or the like). It is recognized that materials with large surface areas can have uptake capabilities at very high suction heights (eg, 100 cm or more). This allows large surface area materials to provide one or both of the following functions. i) Capillary pathway to liquid osmotic absorbent, and / or ii) additional absorption capacity. Thus, although large surface area materials can be described by their surface area per weight or volume, the applicant instead uses the capillarity absorption capacity herein to describe large surface area materials. This is because the capillary adsorption capacity is generally a performance parameter that provides the suction capacity necessary to provide the absorbent member of the present invention with an improved absorbent product. It is recognized that certain high surface area materials, such as glass microfibers, by themselves do not exhibit a particularly high capillary absorption capacity at all heights, especially at very high heights (eg, 100 cm and above). It will be. Nonetheless, such materials are desirable for hydrogel-forming absorbent polymers or other osmotic absorbents when combined with hydrogel-forming absorbent polymers or other osmotic absorbents, which is desirable for hydrogel-forming absorbent polymers or other osmotic absorbents. And may provide the necessary capillary adsorption capacity.
[0053]
Any material with sufficient capillary adsorption capacity will be useful in the storage absorbent member of the present invention when used in combination with a hydrogel-forming absorbent polymer or other osmotic absorbent. In this context, the term “high surface area material” is used by itself (ie when measured without including any other optional materials that make up the osmotic absorbent or storage absorbent member): Any material that exhibits one or more of the capillarity absorption capacity. (I) Capillary at least about 2 g / g, preferably at least about 3 g / g, even more preferably at least about 4 g / g, and even more preferably at least about 6 g / g at a height of 100 cm, with a suction height of 100 cm Adsorption capacity; (II) Capillary adsorption capacity of at least about 5 g / g, preferably at least about 8 g / g, more preferably at least about 12 g / g at a height of 35 cm; (III) At least about at a height of 50 cm Capillary adsorption / absorption capacity of 4 g / g, preferably at least about 7 g / g, more preferably at least about 9 g / g; (IV) at least about 1 g / g at a height of 140 cm, preferably at least about 2 g / g, more preferably Is at least about 3 g / g, even more preferably at least about 5 g / g capillary adsorption capacity; or (V) 200 cm A capillary adsorption capacity of at least about 1 g / g in height, preferably at least about 2 g / g, more preferably at least about 3 g / g, even more preferably at least about 5 g / g.
[0054]
In one embodiment, the high surface area material is fibrous in character (hereinafter “high surface area fibers”) and is a fibrous web or fiber when combined with a hydrogel-forming absorbent polymer or other osmotic absorbent. Will result in a matrix. Instead, and in a particularly preferred embodiment, the high surface area material will be an open cell hydrophilic polymer foam (hereinafter "large surface area polymer foam" or more generally "polymer foam"). These materials are described in detail below.
[0055]
1. Large surface area fiber
High surface area fibers useful in the present invention include naturally occurring (modified or non-modified) fibers and synthetically produced fibers. High surface area fibers have a much larger surface area than fibers typically used in absorbent products, such as wood pulp fibers. The high surface area fibers used in the present invention will desirably be hydrophilic. As used herein, the term “hydrophilic” refers to a fiber or surface of a fiber that is wetted by an aqueous liquid (eg, aqueous body fluid) deposited on these fibers. Hydrophilicity and wettability are typically defined by the contact angle and surface tension between the liquid and solid involved. This is because Robert F. et al. It is discussed in detail in an American Chemical Society publication (Copyright 1964) entitled “Contact Angle, Wettability and Adhesion” edited by Gould. The fiber or the surface of the fiber has a contact angle between the liquid and the fiber or its surface of less than 90 °, or when the liquid tends to spread naturally across the surface of the fiber (both states are usually co-existing) In either case, it is said to be wetted (ie hydrophilic) by the liquid. Conversely, a fiber or its surface is considered hydrophobic if the contact angle is greater than 90 ° and the liquid does not spread naturally across the surface of the fiber. The hydrophilic nature of the fiber useful herein may be unique to the fiber, or it may be a fiber that is originally a hydrophobic fiber but treated to make it hydrophilic. Materials and methods for imparting hydrophilic properties to inherently hydrophobic fibers are well known.
[0056]
High surface area fibers useful herein will have a capillary suction specific surface area in the same range as the polymer foam described below. However, typically high surface area fibers are characterized based on the well-known BET surface area.
[0057]
High surface area fibers useful herein include glass ultrafine fibers such as glass wool available from Evanite Fiber Corp. (Corvallis, Oregon). Glass ultrafine fibers useful herein will typically have a fiber diameter of less than about 0.8 μm, more typically from about 0.1 μm to about 0.7 μm. These ultrafine fibers are at least about 2 m ² / G, preferably at least about 3 m ² / G surface area. Typically, the surface area of the glass microfiber is about 2 m. ² / G to about 15m ² / G. A typical glass ultrafine fiber used here is available from Evanite Fibers as type 104 glass fiber and has a nominal fiber diameter of about 0.5 μm. These glass ultrafine fibers are about 3.1m ² / G surface area calculated.
[0058]
Another type of high surface area fiber useful herein is fibrillated cellulose acetate fiber. These fibers (referred to herein as “fibrets”) have a large surface area compared to cellulose-derived fibers commonly used in the technical field of absorbent products. Such fibrets have very small diameter regions such that their particle size is typically about 0.5 to about 5 μm. These fibrets typically have a surface area of about 20 m @ 2 / g. A representative fibrette useful herein as a high surface area material is available as Cellulose Acetate Fibret® from Hoechst Celanese Cop. (Charlotte, NC). For a detailed discussion of fibrets, including their physical properties and methods for their preparation, see “Cellulose Acetate Fibrets: A Fibrillated Pulp With High Surface Area. , "Smith, JE, Tappi Journal, Dec. 1988, p.237; and US Pat. No. 5,486,410 (Groeger et al.), Issued January 23, 1996 (see their respective disclosures). (Incorporated herein by reference).
[0059]
In addition to these fibers, those skilled in the art will recognize that other fibers well known in the absorbent art can be modified to provide high surface area fibers for use herein. Exemplary fibers that can be modified to achieve the high surface area required by the present invention are disclosed in the aforementioned US Pat. No. 5,599,335 (see particularly columns 21-24).
[0060]
Regardless of the nature of the high surface area fibers used, the fibers and osmotic absorbent will be separate materials before being combined. As used herein, the term “discrete” means that the high surface area fibers and osmotic absorbent are each formed prior to being combined to form a storage absorbent member. In other words, the high surface area fibers are not formed following mixing with the osmotic absorbent, nor is the osmotic absorbent formed after combination with the high surface area fibers. Combining the separate respective components ensures that the high surface area fibers have the desired morphology and, more importantly, the desired surface area.
[0061]
2. High surface area polymer foam
Useful high surface area polymer foams are described in several aspects below based on their physical properties. In order to measure some of these properties, it is necessary to analyze the foam in the form of a sheet. Thus, the foam is used in the form of particles, but as long as it is prepared from a pre-formed sheet, physical property measurements are performed on the sheet-like foam (ie before forming the particles). Will be done. If the foam is formed into particles (ie, beads) in situ during the polymerization process, similar foams (in terms of chemical composition, cell size, W: O ratio, etc.) are sheeted for purposes of making these measurements. You may shape | mold.
[0062]
(A) Properties of general polymer foam
High surface area polymer foams useful in the high capillary suction storage and absorbent member of the present invention are known in the art. Particularly preferred foams are those obtained by polymerizing high internal phase water / oil emulsions and are described, for example, in US Pat. No. 5,387,207 and US Pat. No. 5,650,222. Is. Another particularly preferred polymer foam is a co-pending US patent application 09/09/09 filed March 13, 1998 by T. DesMarais et al. Entitled “HIGH SUCTION POLYMERIC FOAM MATERIALS”. / 042,429 (P & G Case 7052) and T. DesMarais et al. Entitled “Absorptive Materials for Distributing Aqueous Liquids” filed March 13, 1998 US patent application Ser. No. 09 / 042,418 (P & G Case 7051), the disclosures of each of which are incorporated herein by reference. (Specific preferred foams described in one or both of these co-pending applications are described in the Examples section below.) Useful polymer foams here are relatively open-celled. It is. This means that many of the individual cells of the foam are in undisturbed communication with neighboring cells. Cells in such a relatively open cell foam structure have an inter-cell opening or “window” that is large enough to allow easy liquid transfer from one cell to another within the foam structure. Is included.
[0063]
These relatively open cell foam structures generally have a reticulated feature with individual cells defined by a plurality of webs that are interconnected and three-dimensionally branched. The strands of polymer material that make up these branched webs can be referred to as “struts”. For the purposes of the present invention, the most preferred foam material will have at least about 80% cells in the foam structure that are at least 1 μm in size and in liquid communication with at least one adjacent cell.
[0064]
In addition to being open-celled, these polymer foams are sufficiently hydrophilic to allow the foam to absorb aqueous liquids. The inner surface of the foam structure is rendered hydrophilic by residual hydrophilizing surfactant remaining in the foam structure after polymerization, or by selected post-polymerization foam treatment methods, as described below. .
[0065]
The degree to which these polymer foams are “hydrophilic” can be quantified by the “adhesion tension” value shown when in contact with an absorbable test solution. The adhesion tension exhibited by these foams can be measured experimentally using a method that measures the uptake weight of a test fluid, such as synthetic urine, for a sample having a known size and capillary suction specific surface area. . Such a method is described in detail in the Test Methods section of US Pat. No. 5,387,207. The foam, which is a high surface area material useful in the present invention, generally has a surface tension of about 65 ± 5 dynes / cm, as measured by capillary suction uptake of synthetic urine, about 15 to about 65 dynes / cm, more preferably It exhibits an adhesion tension value of about 20 to about 65 dynes / cm.
[0066]
The polymer foam useful herein is preferably prepared in a collapsed (ie, unexpanded) form, the polymer foam absorbs such liquid when contacted with aqueous liquid, and the amount absorbed absorbs capillary and confining pressures. Expands below the expansion pressure of the foam (described below). These collapsed polymer foams are usually obtained by squeezing the aqueous phase from the polymerized HIPE foam by compressive force and / or heat drying and / or vacuum dehydration. After compression and / or heat drying and / or vacuum dehydration, these polymer foams become crushed, ie not expanded.
[0067]
A typical collapsed HIPE foam cell structure with water squeezed out by compression is shown in the photomicrographs of FIGS. 3 and 4 of the aforementioned US Pat. No. 5,650,222. As shown in these figures, the cellular structure of the foam is distorted, especially when compared to the expanded HIPE foam structure shown in FIGS. 1 and 2 of the '222 patent. Also, as can be seen from FIGS. 3 and 4 of the '222 patent, voids or pores (dark areas) in the collapsed foam structure are flat or elongated. (It is noted that the foam shown in the '222 patent is in the form of a sheet; as explained below, a foam in the form of a sheet is useful here, but in a preferred embodiment the foam is In the form of particles). Another useful HIPE-derived foam cell structure (in an expanded state) useful herein is shown herein in FIGS. 3 and 4. The preparation of this particular foam and related foams is described herein in Examples 2-4, and these ultra-high surface area foams are entitled “HIGH SUCTION POLYMERIC FOAM MATERIALS”. Co-pending US patent application Ser. No. 09 / 042,429 (P & G Case 7052) filed Mar. 13, 1998 by TADesMarais et al. And “ABSORBENT MATERIALS FOR DISTRIBUTING AQUEOUS LIQUIDS Are described in more detail in co-pending US patent application Ser. No. 09 / 042,418 (P & G Case 7051) filed Mar. 13, 1998 by TADesMarais et al. Which is incorporated herein by reference.
[0068]
Following compression and / or heat drying / vacuum dewatering, the collapsed polymer foam can be re-expanded when wetted by an aqueous liquid. Surprisingly, these polymer foams remain in this collapsed or unexpanded state for a considerable period, for example up to at least about one year. The ability of these polymer foams to remain in this collapsed / unexpanded state is believed to be due to capillary forces, and particularly the capillary pressure generated within the foam structure. As used herein, “capillary pressure” refers to the pressure differential across the liquid / air interface due to the curvature of the meniscus within a narrow range of pores in the foam. [See Chatterjee, “Absorbency” Textile Scienc and Technology, Vol. 7, 1985, p. ]
After compression and / or heat drying / vacuum dehydration to the extent practicable, these polymer foams are absorbed into the hydrated water associated with the hygroscopic hydrate salts incorporated therein and into the foam. Having residual water including both free water. This residual water (assisted by the hydrated salt) is believed to exert capillary pressure on the resulting collapsed foam structure. The collapsed polymer foam of the present invention is at least about 4%, typically about 4% by weight of the foam when stored at 72 ° F. (22 ° C.) and 50% relative humidity ambient conditions. It may have a residual water content of ~ 40%. Preferred collapsed polymer foams have a residual water content of at least about 5 to about 30% by weight of the foam.
[0069]
An important parameter for these foams is their glass transition temperature. Tg represents the midpoint of the transition between the glassy and rubbery state of the polymer. Foams with a Tg above the use temperature can be very strong but will be hard and potentially susceptible to breakage. Also, such foams typically require a long time to return to an expanded state when stored in a collapsed state for an extended period of time and then wet with an aqueous solution that is cooler than the Tg of the polymer. Desirable combinations of mechanical properties, particularly strength and flexibility, typically require a fairly selective range of monomer types and levels to achieve these desired properties.
[0070]
For foams useful in the present invention, the Tg should be as low as possible as long as the foam has acceptable strength at the temperatures in use. Therefore, monomers that give the corresponding homopolymer with lower Tg are selected as much as possible. It has been found that the chain length of alkyl groups on acrylate and methacrylate comonomers can be longer than expected from the Tg of the homologous homopolymer series. Specifically, homologous series of alkyl acrylate or alkyl methacrylate homopolymers have been found to have a minimum Tg with a chain length of 8 carbon atoms. In contrast, the minimum Tg of the copolymer of the present invention occurs with a chain length of about 12 carbon atoms. (Alkyl-substituted styrene monomers can be used in place of alkyl acrylates and alkyl methacrylates, but their availability is currently very limited).
[0071]
It can also be important that the shape of the glass transition region of the polymer, ie whether it is narrow or wide as a function of temperature. The shape of this glass transition region becomes a problem particularly when the temperature of use of the polymer (usually ambient temperature or body temperature) is at or near Tg. For example, a wide transition region may mean that the transition is incomplete at the operating temperature. Typically, if the transition is incomplete at the use temperature, the polymer will exhibit greater rigidity and less flexibility. Conversely, if the transition is complete at the use temperature, then the polymer will show a faster recovery from compression when wetted with an aqueous solution. Thus, it is desirable to control the Tg of the polymer and the width of the transition region to achieve the desired mechanical properties. In general, the Tg of the polymer is preferably at least 10 ° C. below the use temperature. (Tg and width of transition region are derived from loss tangent versus temperature curves from dynamic mechanical analysis (DMA) measurements as described in US Pat. No. 5,565,222).
[0072]
(B) Capillary suction specific surface area
Although large surface area materials have generally been described based on their capillary adsorption capacity, useful large surface area polymer foams can also be described by their capillary suction specific surface area (hereinafter "CSSSA"). Can do. In general, CSSSA is a measure of the surface area that can be contacted by a test solution of a polymer network that forms a particle foam per unit mass of bulk foam material (polymer structural material and solid residual material). Capillary suction specific surface area is determined by both cell unit dimensions within the foam and the density of the polymer, thus quantifying the total amount of solid surface provided by the foam network, to the extent that such surface area contributes to absorbency. Is the method. To characterize the foam useful herein, CSSSA is measured on the foam sheet even when the foam is in the form of particles when the foam is incorporated into a storage absorbent member.
[0073]
Foam CSSSA is related to whether the foam used to prepare the storage absorbent member of the present invention provides the necessary capillary suction. This is because the capillary pressure generated in the foam structure is proportional to the capillary suction specific surface area. In addition, CSSSA is relevant to whether proper capillary pressure is generated within the foam structure and remains crushed until wet with aqueous liquid. Assuming other factors such as foam density and adhesion tension are constant, this means that as CSSSA increases (or decreases), the capillary pressure in the foam structure also increases (or decreases) proportionally. Means.
[0074]
For the purposes of the present invention, CSSSA is determined by measuring the amount of capillary uptake of a low surface tension liquid (eg, ethanol) generated within a foam sample of known mass and dimensions. A detailed description of such a method for determining the specific surface area of a foam is provided in the Test Methods section of US Pat. No. 5,387,207, which is incorporated herein by reference. Any reasonable alternative method for determining CSSSA can be used.
[0075]
The collapsed polymer foam of the present invention useful as an absorbent is at least about 3 m. ² / G CSSSA. Typically, CSSSA is about 3 to about 30 meters. ² / G, preferably about 4 to about 17 m ² / G, most preferably about 5 to about 15 m ² / G. Foam having such a CSSSA value (from about 0.010 to about 0.033 m in the expanded state) ² / Density) will generally have a particularly desirable balance of absorption capacity, liquid retention, and liquid wicking or dispensing characteristics for aqueous liquids such as urine. Furthermore, foams with such CSSSA generate sufficient capillary pressure and can keep the foam in a crushed and unexpanded state until wet with such an aqueous liquid.
[0076]
(C) Capillary pressure and force in the foam structure
As discussed above, particularly preferred collapsible polymer foams, in their collapsed state, are at least equal to the force exerted by the elastic recovery or modulus of the polymer compressed within the foam structure. Capillary pressure is generated. In other words, the capillary pressure required to keep the collapsed foam relatively thin is measured by the opposing force exerted by the compressed polymer foam as it “tries to bounce”. The elastic recovery tendency of the polymer foam is maintained in this compressed state until the expanded foam is compressed to about 1/6 (17%) of its original expanded thickness and then the relaxation stress value is measured. Can be estimated from stress-strain experiments. Instead, for the purposes of the present invention, relaxation stress values are estimated from measurements on polymer foams that are in a collapsed state when in contact with an aqueous liquid such as water. This alternative relaxation stress value is hereinafter referred to as the “expansion pressure” of the foam. The expansion pressure for the collapsed polymer foam of the present invention is about 50 kilopascals (kPa) or less, typically about 7 to about 40 kPa. A detailed description of the method for estimating the expansion pressure of the foam is given in the Test Methods section of US Pat. No. 5,387,207.
[0077]
(D) Free absorption capacity
Another important property of the high surface area polymer foams useful in the present invention is their free absorption capacity. “Free absorption capacity” (or “FAC”) is the total amount of test liquid (synthetic urine) that a given foam sample absorbs into its cell structure per unit mass of solid material in the sample. To be particularly useful in the storage absorbent member of the present invention, the polymer foam has a free absorption capacity of synthetic urine of about 30 to about 100 mL, preferably about 30 to about 75 mL, per gram of dry foam material. Should be. A method for measuring the free absorption capacity of a foam is described below in the test method section of US Pat. No. 5,650,222.
[0078]
(E) Expansion coefficient
When exposed to an aqueous liquid, the preferred collapsed polymer foam absorbs the liquid and expands. Polymer foams absorb more liquid than most other foams in the expanded state. The “expansion coefficient” for these foams is at least about 4 times, ie the thickness of the foam in its expanded state is at least about 4 times the thickness of the foam in its collapsed state. The collapsed foam preferably has an expansion coefficient ranging from about 4 times to about 15 times, more preferably from about 5 times to about 10 times.
[0079]
For the purposes of the present invention, the relationship between the expanded thickness and the collapsed thickness can be empirically predicted from the following equation for a foam that is compressed to remove water.
[0080]
Thickness (expansion) = thickness (crushed) × ((0.133 × W: O ratio) ± 2)
Where the thickness (expansion) is the thickness of the foam in the expanded state;
Thickness (collapse) is the thickness of the foam in the collapsed state;
The W: O ratio is the water / oil ratio of HIPE where the foam is formed. Thus, a typical polymer foam made from an emulsion with a 60: 1 water / oil ratio has an expected expansion coefficient of 8.0, ie an expanded thickness that is 8 times the collapsed thickness of the foam. Will have. The method for measuring the coefficient of expansion is described below in the test method section of US Pat. No. 5,650,222.
[0081]
(F) Compression deflection resistance
A problematic mechanical feature of high surface area polymer foams useful in the present invention is its strength in the expanded state as determined by compression deflection resistance (RTCD). The RTCD shown here by the foam is a function of the modulus of the polymer and the density and structure of the foam network. Next, the elastic modulus of the polymer is determined by: a) the composition of the polymer; b) the conditions under which the foam is polymerized (eg, especially with respect to cross-linking, the complete polymerization obtained); and c) Determined by the degree to which it is plasticized by the emulsifier remaining in the foam structure:
In order to be useful as the high surface area portion of the absorbent member of the present invention, the polymer foam should be suitably resistant to deformation or compression due to forces encountered during use. Foams that do not have sufficient foam strength with respect to RTCD may be under compressive stress caused by the movement and activity of the user of the absorbent product containing the foam, which may provide the necessary capillary suction capacity under unloaded conditions. Will not bring that capacity.
[0082]
The RTCD exhibited by the polymer foam useful in the present invention can be quantified by determining the amount of strain that occurs in a sample consisting of a saturated foam held at a defined temperature and time under a certain confining pressure. Methods for performing this particular type of test are described below in the Test Methods section of US Pat. No. 5,650,222. The foams useful herein are preferably compressed with a confining pressure of 5.1 kPa, typically when compressed to a free absorbent capacity with synthetic urine having a surface tension of 65 ± 5 dynes / cm. An RTCD that produces about 90% or less of the strain will be shown. Preferably, the strain produced under these conditions is about 1 to about 90%, more preferably about 1 to about 25%, even better about 2 to about 10%, more preferably about 2 to about 5%. Would be in the range.
[0083]
(G) Vertical suspension adsorption height
The high surface area polymer foam useful herein can also be described by its vertical suspended adsorption height (hereinafter “VHSH”). The VHSH height in X% is the height (cm) when 0% capacity (ie FAC) X% is retained in the foam. In principle, X can be any value, but an important representative value is VHSH at 90%. The most reproducible measurement for VHSH is achieved with X = 90% within our experience. It will be apparent to those skilled in the art that the numerical value at this point does not adequately represent the shape of the curve obtained by plotting capacity against height. However, this one point serves as a practical comparison point for the foams of the present invention. In this regard, the foam is typically at least about 20 cm, preferably at least about 40 cm, even more preferably at least about 60 cm, even more preferably at least about 70 cm, and even more preferably at least about 80 cm, an equilibrium 90% VHSH. Would have. Typically, preferred polymer foams are about 20 to about 90 cm, more typically about 60 to about 90 cm, more typically about 70 to about 90 cm, and even more typically about 80 to about 90 cm. Of 90% VHSH. The method for measuring 90% VHSH is described in detail in the Test Methods section below. As indicated above, when the high surface area polymer foam is in the form of particles when combined with an osmotic absorbent, 90% VHSH is for the corresponding sheet form of the foam (ie before forming the particles). ) Measured. If foam is formed into particles (ie, beads) during the polymerization process, a similar foam may be formed into a sheet to evaluate 90% VHSH.
[0084]
(H) Other properties of polymer foam
Foam cells, especially cells formed by polymerizing a monomer-containing oil phase surrounding a relatively monomer-free aqueous phase droplet, are often substantially spherical in shape. The size or “diameter” of such spherical cells is a parameter commonly used to characterize foams in general. Since the cells in a given sample of polymer foam are not necessarily approximately the same size, an average cell size, i.e., an average cell diameter, is often specified.
[0085]
Many methods are available to determine the average cell size of the foam. However, the most useful method for determining the cell size in the foam involves simple measurements based on scanning electron micrographs of the foam sample.
[0086]
The cell size measurements given here are based on the number average cell size of the foam in the expanded state, as shown, for example, in FIG. 1 of US Pat. No. 5,650,222. Useful foams according to the present invention will preferably have a number average cell size of about 80 μm or less, typically about 5 to about 50 μm.
[0087]
“Foam density” (ie grams of foam per cubic centimeter of foam in air) is specified here on a dry basis. The amount of water soluble residual material absorbed, such as residual salt and liquid remaining in the foam after HIPE polymerization, washing and / or hydrophilic treatment is ignored when calculating and displaying the foam density. However, the foam density includes other water insoluble residual materials present in the polymerized foam, such as emulsifiers. Such residual material may actually contribute to a significant mass for the foam material.
[0088]
Any suitable gravimetric method that provides a method for determining the mass of solid foam material per unit volume of foam structure can be used to measure foam density. For example, the ASTM gravimetric method fully described by the test method section of US Pat. No. 5,387,207 (Dyer et al.), Issued February 7, 1995, above, can be used for density determination. There are two ways. In the collapsed state, the polymer foam useful in the present invention is about 0.1 to about 0.2 g / cm. ^Three , Preferably about 0.11 to about 0.19 g / cm ^Three And most preferably from about 0.12 to about 0.17 g / cm ^Three Having a dry-based density value in the range of (excluding any residual salt and / or water). In their expanded state, the polymer foam useful herein is about 0.01 to about 0.033 g / cm. ^Three , Preferably about 0.013 to about 0.033 g / cm ^Three Having an anhydrous base density value in the range of
[0089]
Vertical wicking, ie liquid wicking in the direction opposite to gravity, is a desirable performance attribute for the polymer foam useful herein. For the purposes of the present invention, the vertical wicking rate reflects the permeability of the material, and thus the ability of the material to transport liquid to a hydrogel-forming absorbent polymer or other osmotic absorbent.
[0090]
The vertical wicking rate is determined by measuring the time it takes for a colored test solution (eg, synthetic urine) in the reservoir to suck up a 5 cm vertical distance through a test strip of a particular size foam. The vertical wicking method is described in more detail in the test method section of US Pat. No. 5,387,207, but is performed at 31 ° C. instead of 37 ° C. In order to be particularly useful in an absorbent member to absorb urine, foams useful herein will preferably aspirate synthetic urine (65 + 5 dynes / cm) to a height of 5 cm within about 15 minutes. More preferably, the preferred foam absorbent of the present invention draws up synthetic urine to a height of 5 cm within about 10 minutes.
[0091]
The vertical wicking absorption capacity test is the test solution per gram of absorbent foam held in each 1 inch (2.54 cm) vertical section of the same standard size foam sample used in the vertical wicking test. Measure the amount. Such a determination is generally made after the sample is equilibrated to the vertical wicking test solution (eg, after about 18 hours). Similar to the vertical wicking test, the vertical wicking absorption capacity test is more fully described by the test method section of US Pat. No. 5,387,207 (Dyer et al.), Issued February 7, 1995, above. Yes. A high vertical wicking absorption capacity at high height is theoretically equivalent to a high capillary absorption capacity at high height. The foam sheet form useful here is sensitive to the former test, and the former test is easier and cheaper to perform, so the data from the former test is important for this foam of the present invention. It is recommended as a means to specify the parameters.
[0092]
In a particularly preferred embodiment, the polymer foam is in the form of particles, although the high capillary suction foam may be in the form of a sheet when combined with an osmotic absorbent (eg, a hydrogel-forming absorbent polymer). To give a mixture. That is, the foams may be initially prepared in the form of sheets, but these sheets may be treated to provide foam particles, and then the foam may be combined with the hydrogelled polymer. As discussed above, foams useful herein and processes for their preparation are described in US Pat. No. 5,387,207, US Pat. No. 5,650,222, “High Suction Polymer Foam Materials. Copending US patent application Ser. No. 09 / 042,429 (P & G Case 7052) filed Mar. 13, 1998 by TADesMarais et al. Entitled “HIGH SUCTION POLYMERIC FOAM MATERIALS”; A very co-pending US patent application Ser. No. 09 / 042,418 (P & G Case 7051) filed Mar. 13, 1998 by TADesMarais et al. Entitled “Absorptive Materials for Distributing Aqueous Liquids”. It is described in detail. The foam particles are first formed into a sheet-like foam according to the teachings of these references, and then mechanically processed (e.g., crushed, cut, For example, by cutting). Instead, US Pat. No. 5,653,922 issued to Li et al. On August 5, 1997 and US Pat. No. 5,583,162 issued to Li et al. On December 10, 1996 (these Each of which is incorporated herein by reference), the foam particles may be prepared directly from an emulsion in the form of polymer microbeads. Specific examples for making polymer foam / hydrogel-forming polymer blends are discussed in more detail below.
[0093]
When the polymer foam is in the form of particles, the particle size of the separate polymer foam may be very large or very small, and may be a mixture of various particle sizes, especially if the osmotic absorbent is a hydrogel-forming absorbent In the case of a conductive polymer, it depends in part on the size of the osmotic absorbent. Although the dry particle size may be greater than about 1000 microns, it is believed that particles larger than about 1000 microns cannot maintain optimal fluid transport in contact with the osmotic absorbent. Particles that are smaller than about 1000 microns in size, as measured when dry, are believed to contact the osmotic absorbent and provide excellent fluid transport. Also, the dry particle size may be greater than about 50 microns. It is believed that dry particles of mass median particle size less than about 50 microns have a poor cellular structure of polymer foam that provides liquid transport with high suction to the osmotic absorbent. In typical applications, the dry particle size is such that the dry media has a mass median particle size of less than about 600 microns, and typically the dry media has a mass median particle size of about 50 to 600 microns. The dry particle size and the mass median particle size of the dry particles have been previously described in III. A. 1. As discussed in connection with the hydrogel-forming absorbent polymer in the section, it can be determined by subjecting the dry polymer foam to a dry screen through a suitable screen.
[0094]
Applicants have also found that the large surface area foam may optionally contain a liquid so as to increase the transport of urine to the osmotic absorbent of the storage absorbent member. The pre-wetting liquid is thought to partially fill the polymer foam (not intended to be bound by a particular theory) and increase the rate of foam incorporation. Ideally, a polymer foam containing a pre-wetting liquid will prevent microbial growth, prevent loss of volatile water, and store if the water activity is low enough not to migrate away from the foam over time. There should be stability. Water can be used as a prewetting liquid to provide absorption performance, but alone cannot meet other requirements.
[0095]
A preferred method of removing water from the polymer foam particles of one embodiment of the present invention is a unidirectional dehydration method in which the water contained in the wet particles is removed from each particle while the particles are formed. To remove in a single direction. The vacuum dehydration method of Example 5 described below is one example of unidirectional dehydration. The unidirectional dewatering of the preferred granular polymer foam material results in greater expansion of the material when wet than would be achieved without unidirectional dehydration, and this expansion is also due to the penetration of the osmotic absorbent into the polymer. As the fluid from the foam is absorbed and as the polymer foam absorbs the fluid, further contact between the polymer foam and the osmotic absorbent material is provided.
[0096]
C. Optional ingredients and materials
The storage absorbent member according to the present invention may include other optional ingredients that may be present in the absorbent web. For example, a reinforcing scrim can be placed inside the storage absorbent member or between each absorbent member of the absorbent core. Such reinforcing scrims must be structured so as not to form an interfacial barrier against liquid movement, especially when placed between the respective absorbent members of the absorbent core. In addition, some binders may be used to provide dry and wet integrity to the absorbent core and / or the absorbent storage member itself. In particular, hydrophilic adhesive fibers may be used to provide a bond between the large surface area material and the osmotic absorbent material. This is particularly important for granular high surface area materials. The amount of binder used is preferably as small as possible so as not to impair the capillary adsorption properties of the absorbent member. However, those skilled in the art will recognize that there are also binders that can enhance the capillary adsorption properties of the absorbent member, such as a fiberized hydrophilic adhesive having a sufficiently high surface area. In this case, the high surface area hydrophilic adhesive can provide both liquid processing and integrity functions in one material. Also, envelop each absorbent member or the entire absorbent core in a liquid permeable sheet, such as tissue paper sheet, to raise user concerns regarding the free granular absorbent polymer unless capillary continuity is interrupted. It can also be prevented.
[0097]
Other optional components that can be included are materials to control odor, contain stool, and the like. Also, any absorbent member that includes a particulate osmotic absorbent or a large surface area material, or the entire absorbent core is encased in a liquid permeable sheet, such as a tissue paper sheet, and the user's Concerns can also be prevented.
[0098]
IV. Materials and properties of other storage and absorption members
The high capillary suction absorption capacity storage absorbent member of the present invention includes an osmotic absorbent (eg, a hydrogel-forming absorbent polymer as described above) and a large surface area material, and has other optional ingredients such as a thermoplastic material. You may or may not have. (A non-exhaustive list of optional materials useful for the member is described below.) These high suction capacity absorbent members can function as liquid storage members in the absorbent core. The primary function of such a fluid storage member is under the pressure normally encountered as a result of the wearer's movements, either directly or after absorbing bodily fluids drained from other absorbent members (eg, liquid capture / distribution members). Even to retain such fluids. However, it should be understood that such absorbent members can perform functions other than liquid storage.
[0099]
The amount of hydrogel-forming absorbent polymer or other osmotic absorbent contained in the absorbent member can vary considerably. Furthermore, the concentration of the hydrogel can vary throughout the member. In other words, one member may have regions of relatively high and relatively low hydrogel concentrations. Without intending to be bound by theory, the minimum amount of large area material mixed with the hydrogel-forming absorbent polymer or other osmotic absorbent is the hydrogel-forming absorbent polymer particles or other osmotic particles in dry and wet conditions. It is believed that the absorbent interstitial space must be filled to a functional extent and sufficient to provide capillary continuity and sufficient liquid flow to the hydrogel-forming absorbent polymer.
[0100]
In a preferred embodiment where the osmotic absorbent is in the form of a hydrogel-forming absorbent polymer, to measure the concentration in a given area of the absorbent member, any other component present in the area containing the hydrogel-forming polymer and hydrogelling polymer ( For example, the weight percent of hydrogel-forming polymer is used relative to the total weight of fiber, polymer foam, etc.). In view of this, the concentration of the hydrogel-forming absorbent polymer in a predetermined region of the absorbent member of the present invention is at least about 50%, at least about 60%, at least about 70%, at least about the total weight of the absorbent member It can be about 80%, or at least about 90%. (The same range applies when other osmotic absorbents are used).
[0101]
Despite the fact that the area of the absorbent member may contain a relatively high concentration of hydrogel-forming absorbent polymer or other osmotic absorbent, it is essentially fibrous in a large surface area material, The member includes at least 25% by weight of large area fibers on a total basis (ie, the total weight of the hydrogel-forming absorbent polymer used in the member divided by the total weight of the absorbent member multiplied by 100%). Will. A lower limit of about 25% fiber is considered necessary to provide the necessary capillary suction for the absorbent member. Preferably, the storage absorbent member will comprise at least about 30% by weight high surface area fibers, more preferably at least 35% by weight. The absorbent members of the present invention are typically about 25 to about 90 wt%, more typically about 30 to about 85 wt%, and even more typically about 35 to about 80 wt% on an aggregate basis. Of high surface area fibers.
[0102]
In embodiments where the high surface area material is a polymer foam, the absorbent member preferably comprises at least about 1% by weight (based on total) polymer foam. The ability to use very low levels of polymer foam relative to the amount of high surface area fibers described above is the very low density of these foams, the fact that the foam is open-celled, the foam It is thought to be due to various factors including itself contributing to the overall absorption capacity. The storage absorbent member will preferably contain at least about 10% by weight, more preferably at least about 15% by weight, and even more preferably at least about 20% by weight polymer foam. Typically, such storage absorbent members are about 1 to about 98% by weight, more typically about 10 to 90% by weight, even more typically about 15 to about 85% by weight, even more Typically, it will contain from about 20 to about 80% polymer foam material by weight. As explained above, these weight percent ranges are based on the total weight of the respective materials in the absorbent member. It has been found that the area of the absorbent member may contain more and less material.
[0103]
Of course, the relative levels of the osmotic absorbent (eg, hydrogel-forming absorbent polymer) and the large surface area material are determined by, for example, the absorbent capacity of the osmotic absorbent, the specific large surface area material used, the nature of the large surface area material (eg, sheet or Particle foam, particle size) and the like. In this regard, a high level of osmotic absorbent provides an absorbent member for producing a thin absorbent body to achieve the required level of capillary suction described above, but is sufficient to provide such a suction capacity. There must be a large surface area material. Without intending to be bound by theory, the three main properties of the preferred collapsible polymer foam materials described above allow these foams to function particularly effectively in highly absorbent storage absorbent members. I think that. These three properties are: (i) a relatively low density, (ii) the ability to easily distribute liquid within itself, and (iii) remain crushed, but then the preferred hydrogel-forming absorbent polymer When it swells by absorbing liquid, it has the ability to absorb and swell with sufficient liquid. The latter property maintains contact between the foam material and the hydrogel-forming particles as a fluid absorbing member.
[0104]
A representative storage-absorbing member of the present invention is shown by the micrographs of FIGS. Referring to FIG. 5, a particulate hydrophilic polymer foam material, indicated at 102, and a particulate hydrogel-forming absorbent polymer, indicated at 106, are in contact with each other. Also indicated and shown as 110 is an adhesive filament, which provides structural integrity and maintains contact between the foam particles 102 and the hydrogel-forming polymer particles 106. Referring to FIG. 6, a single hydrogel-forming polymer 116 is surrounded by a number of fibrets, generally indicated as 114. Finally, in FIG. 7, a single hydrogel-forming polymer 126 is surrounded by a plurality of glass fibers, generally indicated as 125.
[0105]
In addition to the high surface area material and the hydrogel-forming absorbent polymer, the storage absorbent member of the present invention may contain other optional materials. For example, the storage absorbent member may contain an adhesive or binder material to provide the integrity of the required mixture of materials. Such materials are particularly desirable when the high surface area material is essentially granular.
[0106]
When introducing integrity with a binder material, suitable binders are, for example, meltblown adhesives described in US Pat. No. 5,560,878 (issued to Dragoo et al., Oct. 1, 1999). The disclosure of which is incorporated herein by reference. The method of combining meltblown adhesive with the required hydrogel-forming absorbent polymer and high surface area material is also described in detail in the '878 patent.
[0107]
In an absorbent member containing a mixture of hydrogel-forming polymer and high surface area fibers and / or particulate polymer foam, as another example of a material that provides the integrity of the mixture, the member may contain a thermoplastic material. Upon melting, at least a portion of this thermoplastic material moves to the intersection of the respective member elements, typically due to capillary gradients between particles or fibers. These intersections become binding sites for the thermoplastic material. When cooled, the thermoplastic material at these intersections cures to form a binding site that holds the matrix of material together.
[0108]
The optional thermoplastic material useful herein may be in any of a variety of forms including particles, fibers, or a combination of particles and fibers. Thermoplastic fibers are a particularly preferred form because of their ability to form numerous binding sites. Suitable thermoplastic materials may consist of any thermoplastic polymer that can be melted at a temperature that does not extensively damage the material comprising the absorbent member. Preferably, the melting point of the thermoplastic material is less than about 190 ° C, and preferably between about 75 ° C and about 175 ° C. In any event, the melting point of the thermoplastic material should not be lower than the temperature at which the thermally bonded absorbent structure would be stored when used in an absorbent product. The melting point of the thermoplastic material is typically about 50 ° C. or higher.
[0109]
Thermoplastic materials, in particular thermoplastic fibers, are for example polyolefins such as polyethylene (for example PULPEX® and polypropylene, polyesters, copolyesters, polyvinyl acetate, polyvinyl acetate, polyvinyl chloride, polyvinylidene chloride, polyacrylate, It may consist of various thermoplastic polymers including polyamide, copolyamide, polystyrene, polyurethane and any of the above copolymers such as vinyl chloride / vinyl acetate, etc. One preferred thermoplastic binder fiber is PLEXAFIL (registered trademark) polyethylene ultrafine fiber (manufactured by DuPont), which is an 80% cellulosic fiber sold under the trademark KITTYHAWK (registered trademark) (manufactured by Weyerhaeuser CO.) Depending on the properties desired for the resulting heat-bonded absorbent member, suitable thermoplastic materials may be hydrophilic fibers such as polyolefins such as polyethylene or polypropylene, poly Including thermoplastic fiber treated with surfactant or silica, derived from acrylic, polyamide, polystyrene, polyurethane, etc. The surface of hydrophobic thermoplastic fiber is surface active like nonionic or anionic surfactant Treatment with agents, for example, spraying a surfactant on the fiber, dipping the fiber in the surfactant, or including the surfactant as part of the dissolved polymer when making the thermoplastic fiber The surfactant can be made hydrophilic by melting and re-solidifying. Suitable surfactants include nonionics such as Brij® 76 manufactured by ICI Americas, Inc. of Wilmington, Delaware. And various surfactants sold under the trademark Pegosperse® by Glyco Chemical, Inc. of Greenwich, Connecticut. In addition to surfactants, anionic surfactants can also be used, and these surfactants can be applied to thermoplastic fibers at a level of, for example, about 0.2 to about 1 g per square centimeter of thermoplastic fiber.
[0110]
Suitable thermoplastic fibers may be a single polymer (monocomponent fibers) or may be composed of more than one polymer (eg bicomponent fibers). As used herein, “bicomponent fiber” means a thermoplastic fiber having a core fiber made of one polymer and encased in a thermoplastic sheath made of different polymers. The polymer making up the sheath often melts at a lower temperature, typically at a lower temperature, than the polymer making up the core. As a result, these bicomponent fibers provide thermal bonding due to melting of the sheath polymer while retaining the desirable strength properties of the core polymer.
[0111]
Suitable bicomponent fibers for use in the present invention include sheath / core fibers having the following polymer combinations: Polyethylene / polypropylene, polyethyl vinyl acetate / polypropylene, polyethylene / polyester, polypropylene / polyester, copolyester / polyester, etc. Particularly suitable bicomponent thermoplastic fibers for use herein are those having a polypropylene or polyester core and a lower melting point copolyester, polyethyl vinyl acetate or polyethylene sheath (eg, DANAKLON®, CELBOND). (Registered trademark) or CHISSO (registered trademark) bicomponent fiber). These bicomponent fibers may be concentric or eccentric. As used herein, the terms “concentric” and “eccentric” refer to whether the sheath has a uniform or non-uniform thickness through the cross-section of the bicomponent fiber. Eccentric bicomponent fibers are preferred because the fiber thickness is smaller and provides higher compressive strength. Suitable bicomponent fibers used herein may be not crimped (ie, not bent) or may be crimped (ie, may be bent). Bicomponent fibers are typically crimped by typical textile means such as, for example, a stuffer box method or gear crimp method to achieve primarily two-dimensional or “flat” crimping. it can.
[0112]
In the case of thermoplastic fibers, their length can vary depending on the specific melting point and other properties desired for these fibers. Typically, these thermoplastic fibers have a length of about 0.3 to about 7.5 cm, preferably about 0.4 to about 3.0 cm, and most preferably about 0.6 to about 1.2 cm. Have. Moreover, the characteristics including the melting point of these thermoplastic fibers can be adjusted by changing the fiber diameter (caliper). The diameter of these thermoplastic fibers is typically defined by either denier (grams per 9,000 meters) or decitex (grams per 10,000 meters). Suitable bicomponent thermoplastic fibers may have a decitex in the range of about 1.0 to about 20, preferably about 1.4 to about 10, and most preferably about 1.7 to about 3.3. .
[0113]
The compression modulus of these thermoplastic materials, particularly thermoplastic fibers, can also be important. The compressive modulus of thermoplastic fibers is not only their length and diameter, but also the polymer or composition of the polymer from which they are made, the shape and structure of the fiber (eg concentricity or eccentricity, crimps that are crimped) It is also affected by factors such as The difference in compression modulus of these thermoplastic fibers can be used to change the properties of each absorbent member, and in particular the density properties, during the preparation of the absorbent core.
[0114]
Other materials known in the art may also be included in the absorbent storage material provided that they are included at a sufficiently low level to achieve the necessary capillary suction characteristics. An optional material that may be included in the storage member of the present invention is a fibrous material that is usually combined with a hydrogel-forming absorbent polymer. For example, wood-based fibers may be included in the same manner as synthetic fibers. However, since such materials tend to reduce the capillary suction capacity of storage members comprising high surface area materials and hydrogel-forming absorbent polymers, they are relatively low so that the member still provides the desired capillary suction capacity. Included by level. In fact, it is preferable to exclude the use of such fibers as long as they are added in bulk to reduce the capillary absorption capacity on a weight basis.
[0115]
Many methods known in the art can be used to combine a hydrogel-forming polymer (or other osmotic absorbent) with a high surface area material. Of course, the physical form (eg, fibrous, granular, etc.) of the high surface area material and hydrogel-forming absorbent polymer will determine which method is used to form the specific storage absorbent member embodiment, at least in part.
[0116]
In one embodiment, the hydrogel-forming absorbent polymer particles are affixed to the fibrous material to prevent unwanted particle migration during manufacture, storage and / or wear. Adhering the absorbent particles to the molten polymer material is described in European Patent Publication EP 156,160, in which the molten polymer material is extruded to create a meltblown polymer microfiber, while they are still sticky. The absorbent particles are put into it to adhere them to the fibers.
[0117]
A method for incorporating particulate absorbent material into a meltblown web is described in U.S. Pat. No. 4,923,454 (in which ultrafine fiber-containing polymers and absorbent products, as well as wetblown hydrophilic nylon meltblown ultrafine fibers and Hydrogel-forming polymer particles are disclosed), and U.S. Pat. No. 4,773,903, in which meltblown microfibers, hydrogel-forming polymer particles, crimped staple fibers and hydrophilizing reagents are disclosed. Are disclosed). The disclosures of these patents are incorporated herein by reference.
[0118]
High surface area materials and hydrogel-forming absorbent polymers can also be incorporated by the methods generally described in 4,764,325, which is incorporated herein by reference.
[0119]
The base weight of the storage absorbent member of the present invention is not critical and will vary depending on the end use of the member (i.e., for example, feminine hygiene products, infant diapers, adult incontinence products, or bandages), Typically about 5 to about 3000 g / cm ² Or about 40 to about 2500 g / cm ² Or about 100 to about 2000 g / cm ² Or about 150 to about 1500 g / cm ² Or about 250 to about 1000 g / cm ² Having a base weight of
[0120]
As explained, particularly preferred storage and absorption members are those used as high capillary suction polymer foam large river surface area materials. In one embodiment, the polymer foam is in the form of particles and is mixed with the particulate hydrogel-forming absorbent polymer to form a homogeneous mixture. FIG. 10 is a schematic block diagram of an apparatus 320 for producing such a homogeneous mixture. Referring to FIG. 10, to prepare the absorbent member, a particulate polymer foam is introduced from a first source 301 to a first metering device 302 (optionally, the device 302 is a metered particulate foam, A fluidized bed loss weight system that controls the amount to the line based on the weight difference from the device over a specified period of time), introducing particulate hydrogel-forming polymer from the second source 303 to the second metering device 304 (Optionally, device 304 is a weight / loss weighing system commonly used in commercial manufacturers of diapers and feminine hygiene napkins; for example, a weight / loss weighing system available from Acrison, Moonachi, NY. This process sets the base weight of the hydrogel-forming polymer in the product). Polymer foam particles and hydrogel-forming polymer particles are introduced into a single mixing chamber 305. Within the mixing chamber 305, a homogeneous mixture of the two components is made. This mixture is then transported through the fibrous adhesive stream emanating from 307 using an air stream 306 (using, for example, a Venturi Dactor to increase the kinetic energy of the particles). Instead, one of the foam and hydrogel-forming polymers can be produced by any technique that can produce a relatively homogeneous mixture and bind or bind the materials together to obtain a free-flowing mixture that is introduced into the air stream 306. Parts may be “aggregated”. The fibrous adhesive stream may be introduced via a melt blow adhesive system such as that available from J & M Laboratories, Dawsonville, GA. The fibrous adhesive stream entangles the polymer foam particles and the hydrogel-forming polymer to form a composite, generally designated 308. For example, in the inlet chamber of a Venturi Dactor at Fox (Dover, NJ), it is considered that homogenous mixing can be achieved. If homogenous mixing is not feasible in chamber 305, two separate transport streams may be required to bring the particulate foam and particulate hydrogel-forming polymer together with the fibrous adhesive transported from 307. Absent). Thereafter, the composite material 308 is optionally placed between the first web 309 introduced via the device 309 and the second web 310 introduced via the device 310 to provide the absorbent storage member 311. Form. Thereafter, the entire absorbent storage member 311 may be compressed (eg, using a rotary nip) to achieve the target density and thickness of the member.
[0121]
A process similar to that described in the previous paragraph can be used to combine high surface area fibrettes with an osmotic absorbent (eg, a particulate hydrogel-forming absorbent polymer). In other words, the fibrette may be introduced via a device similar to the first supply source 301 shown in FIG. Other well known methods for combining fibers and hydrogel-forming polymers may be used. A typical means for adjusting such a composite is illustrated in Example 1 below.
[0122]
An alternative method of mixing and accelerating particulate polymer foam and hydrogel-forming polymer utilizes electrostatic forces. In this embodiment, the two materials are “charged” and generate an attractive force between them. This force is used to create a homogenous mixture of the two materials, potentially creating a driving force that accelerates the blend through the adhesive stream, thus eliminating one of the process air streams. .
[0123]
In other preferred embodiments, a particulate hydrogel-forming absorbent polymer is disposed between two polymer foam sheets. Thereafter, the layered laminate is manipulated in the machine direction and / or cross direction (for example, by completely cutting its thickness) to separate the sheet into strips or pieces, and the storage absorbent member consisting of small sections of the layered laminate give. (Note that the layered structure formed prior to cutting is also useful as a storage absorbent member and can provide advantages for commercial scale manufacturing. However, applicants have further processed it at higher suction heights. It was found that a storage absorbent member having a particularly high capillary absorption capacity can be provided). FIG. 11 shows an apparatus for making such a layered laminate, and FIG. 12 shows a cut layered laminate that can be used as the absorbent storage member of the present invention. Referring to the apparatus 420 shown in FIG. 11, a first stretch sheet of polymer foam sheet 402 is weighed by any means known in the art. Separately, the particulate hydrogel-forming absorbent polymer is metered by a metering device 403 (optionally device 304 is a weight / loss metering system commonly used in commercial manufacturers of diapers and feminine hygiene napkins; A weight / loss weighing system available from Moonachi, NY). The hydrogel-forming polymer is weighed and placed in an accelerator 404 (eg, a Flexisplay® type system available from Venturi Dactor or fluidized bed, eg, Nordson, Atlanta, GA), and fiber carried from 405 by air flow Transported towards quality (preferably hydrophilic) adhesive 406 (e.g. Cycloflex® 34-5552 from National Starch, Bridgewater, NJ). The fibrous adhesive entangles the hydrogel-forming polymer particles and immobilizes them to form a mixture 407. Weigh the second polymer foam stretch sheet 408 slightly downstream from where the fibrous adhesive and the hydrogel-forming polymer come together. The momentum of the particle / adhesive mixture 407 carries the mixture to the nip point 409 and the sheets 402 and 408 are laminated. This results in a layered composite 410 having a layer of hydrogel-forming polymer and adhesive sandwiched between two sheets of polymer foam material. Thereafter, the composite 410 is laminated with the nonwoven material 411, and this laminate is introduced into the folding board 412. This superimposes nonwoven 411 around composite 410 (preferably an “e” fold). (The nonwoven material provides integrity to the composite during the next reforming operation and further integrity to the final structure). Thereafter, the wrapped composite is introduced into the first reforming device 413 and the second reforming device 414. In the reformers 413 and 414, the wrapped composite is selectively separated by applying shear planes in a number of directions. The shear surface tears the wrapped composite into a column consisting of a polymer foam and a hydrogel-forming polymer / fibrous adhesive layer. This reforming operation also includes a nonwoven near the shear surface, reducing the base weight of the composite.
[0124]
In order to fully understand the physical characteristics of the preferred composite formed by the above operation, FIG. 12 shows in detail composite 410 after undergoing reforming in devices 413 and 414 (nonwoven wrap is Not shown). In this embodiment, one reforming device completely cuts the entire thickness in the cross direction into several strips, and the other reforming device completely removes the composite in the machine direction. Disconnect. The result is a composite consisting of a number of separate layered columns designated 451. One of these columns 451 is shown in an enlarged view in FIG. This figure shows that each column 451 includes a hydrogel-forming particle, indicated by 452, and a fibrous adhesive, indicated by 453, sandwiched between “cubes” 454 and 455 made of polymer foam material. It is clearly shown. Light blending may be added to the composite 410 during and / or after reforming in the devices 413 and 414 to reinforce the interface between the hydrogel-forming absorbent polymer and the polymer foam material.
[0125]
V. Absorption product
The highly absorptive storage absorbent members of the present invention are particularly useful as storage parts for absorbent structures (eg, absorbent cores or core elements) for various absorbent products. As used herein, an “absorbent product” refers to a significant amount of other fluids (ie, liquids) such as urine, menses, or aqueous feces (fluid defecation) that are excreted by the incontinence wearer or user of the product. ) Means a consumer product that is capable of absorbing. Examples of such absorbent products include disposable diapers, incontinence clothes, sanitary products such as tampons and sanitary napkins, disposable training pants, bed pads and the like. The storage absorbent member herein is particularly suitable for use in products such as diapers, incontinence pads or clothing, clothing shields, and the like.
[0126]
In its simplest form, the absorbent product of the present invention need only contain the storage absorbent member of the present invention, but is typically a relatively liquid impervious backing sheet, and a highly absorptive storage member. including. In other simple forms, the absorbent product need only include a backing sheet, a capture material, and a highly suctionable storage member. The elements are coupled so that the capture material captures the liquid discharge of the absorbent product wearer. The high suction member described herein is arranged in liquid communication with a capture member or any liquid dispensing member that is in liquid or capillary communication with the capture member. The liquid impervious backing sheet is made of any material, such as polyethylene or polypropylene, having a thickness of about 1.5 mils (0.038 mm) to help retain the liquid in the absorbent product. It may be.
[0127]
More usually, these absorbent products also include a liquid permeable topsheet element that covers the side of the absorbent product that touches the wearer's skin. In this configuration, the product includes an absorbent core having one or more liquid storage absorbent members of the present invention located between the backing sheet and the topsheet. The liquid permeable topsheet is made of any material such as polyester, polyolefin, rayon, etc. that is substantially porous and allows body fluids to pass easily through the underlying absorbent core. Also good. The topsheet material preferably does not have a tendency to retain aqueous liquid in the contact area between the topsheet and the wearer's skin.
[0128]
In addition to the storage absorbent member of the present invention, the absorbent core of the absorbent product herein may comprise other, eg, conventional elements or materials. In one embodiment comprising a combination of an absorbent member here and other absorbent material herein, the absorbent product comprises one or more core layers comprising one or more storage absorbent members of the present invention comprising other absorbent structures or materials 1 or A multilayer absorbent core configuration may be used that can be used in combination with further additional separate core layers. These other absorbent structures or materials may include, for example, air-borne or wet-laid webs of wood pulp or other cellulosic fibers. These other absorbent structures are also disclosed, for example, in US Pat. No. 5,563,179 (Stone et al.) Issued Oct. 8, 1996, the disclosure of which is incorporated herein by reference. It may also include an absorbent foam useful as a liquid capture / distribution member, such as those or a foam such as a sponge.
[0129]
Preferred embodiments involve further separation of the various absorbent core elements. This preferred absorbent core has a trapping layer only around the wearer's crotch to handle the initial rapid liquid ejection. The distribution layer is positioned vertically before and after the acquisition layer so as to draw liquid from the crotch. The storage layer is placed in a position near the front and back of the waist and only contacts the dispensing material. The storage absorbent member must be able to absorb the liquid from the distribution layer by overcoming both the force due to gravity and the force due to the desorption pressure of the distribution material. The product so depicted removes liquid from the crotch in the time given during incontinence, leaving the capture area relatively dry and ready for further liquid uptake. This further maintains the shape of the garment and keeps the crotch relatively dry for better skin health. Co-pending US Patent Application No. 08 / 825,072 (filed by G. Young et al. On March 27, 1997), Co-pending US Patent Application No. 08 / 825,071 (March 27, 1997) See also filed by G. LaVon et al.) And co-pending US patent application Ser. No. 08 / 826,208 (filed by G. Young et al. On March 27, 1997). These are incorporated herein by reference.
[0130]
FIG. 1 shows a preferred embodiment of a diaper 60 in which the topsheet 61 and the backsheet 62 are coextensive and have a length and width dimensions that are generally greater than the dimensions of the absorbent core 28. The top sheet 61 is combined with the back sheet 62 and is stacked on the back sheet 62, thereby forming the periphery of the diaper 60. The perimeter defines the outer perimeter or edge of the diaper 60.
[0131]
The top sheet 61 is compliant, has a soft feel, and does not irritate the wearer's skin. Furthermore, the topsheet 61 is liquid permeable, allowing the liquid to easily penetrate its thickness. Suitable topsheets 61 are porous foams, reticulated foams, perforated plastic films, natural fibers (eg wood or cotton fibers), synthetic fibers (eg polyester or polypropylene fibers) or natural and synthetic fibers. It can be made from a wide range of materials such as combinations. Typically, the topsheet 61 is made of a hydrophobic material (initially treated to become hydrophilic) to isolate the wearer's skin from the liquid in the absorbent core 10. The hydrophilic treatment causes the initial wettability of the topsheet and allows the liquid discharge to pass through the topsheet. A particularly preferred topsheet 61 is Hercules, Inc. of Wilmington, Del. Including staple length polypropylene fibers having a denier of about 1.5, such as Hercules type 151 polypropylene sold by As used herein, the term “staple length fiber” refers to a fiber having a length of at least about 15.9 mm (0.62 inches).
[0132]
There are a number of manufacturing techniques used to manufacture the topsheet 61. For example, the top sheet 61 can be a woven fabric, a non-woven fabric, a spun-bonded fabric, a cotton wool fabric, or the like. Preferred topsheets are carded and thermally bonded by means well known to those skilled in the fabric art. Preferably, the topsheet 61 has a weight of about 18 to 25 grams per square meter, a minimum dry tensile strength of at least about 400 grams per centimeter in the machine direction, and a wet tensile strength of at least about 55 grams per centimeter in the cross machine direction. Have.
[0133]
It is preferred but not necessary to have the topsheet as the closest material to the wearer's skin. Appropriate absorbent core shapes could be used without a topsheet and would also provide desirable results such as comfort and absorbency as well as manufacturing simplicity and material cost savings. For example, the body side surface of the absorbent core itself could be made of a liquid permeable, flexible, compliant, non-irritating material that replaces another topsheet. Such an absorbent core would only need to be used in combination with the backsheet to provide comfort and absorbency in the absorbent product.
[0134]
The backsheet 62 is preferably impermeable to liquid and is preferably manufactured from a thin plastic film, although other flexible liquid impermeable materials may also be used. The backsheet 62 is absorbed in the absorbent core 10 and prevents exudates contained therein from wetting products that come into contact with the diaper 60 such as bed sheets and underwear. Preferably, the backsheet 62 is about 0.012 mm (0.5 mil) to about 0.051 centimeters (2.0 mils) thick, although other flexible liquid-impermeable materials may be used. A polyethylene film having As used herein, the term “flexible” refers to a material that is compliant and easily conforms to the general shape and contours of the wearer's body.
[0135]
A suitable polyethylene film is manufactured by Monsanto Chemical Corporation and sold under the name film number 8020. The backsheet 62 is preferably embossed and / or matte finished to give it a more cloth-like appearance. Further, the backsheet 62 may be “breathable”, allowing vapor to exit the absorbent core 28 while still preventing exudates from passing through the backsheet 6. A backsheet that is highly breathable but substantially impermeable to liquids may be desirable for certain absorbent products.
[0136]
The size of the backsheet 62 is defined by the size of the absorbent core 28 and the actual diaper design selected. In a preferred embodiment, the backsheet 62 has the absorbent core 28 at a minimum distance of at least about 1.3 centimeters to at least about 2.5 centimeters (about 0.5 to about 1.0 inches) around the entire diaper. It has a deformed hourglass shape that extends beyond it.
[0137]
The topsheet 61 and the backsheet 62 are joined together in any suitable manner. As used herein, the term “joined” means that the topsheet 61 is directly bonded to the backsheet 62 by fixing the topsheet 61 directly to the backsheet 62 and the topsheet 61 is intermediate. It includes a shape in which the top sheet 61 is indirectly bonded to the back sheet 62 by being fixed to the member and then being fixed to the back sheet 62. In a preferred embodiment, the topsheet 61 and the backsheet 62 are secured directly to each other around the diaper by an attachment means (not shown) such as an adhesive or any other attachment means known in the art. For example, a uniform continuous layer of adhesive, a patterned layer of adhesive, or an array of separate lines or points of adhesive can be used to secure the topsheet 61 to the backsheet 62.
[0138]
The tape tab fastener 65 is typically applied to the waistband region 63 of the diaper 60 to provide a fastening means for holding the diaper to the wearer. The illustrated tape tab fastener 65 is merely exemplary. The tape tab fastener is any of those known in the art, such as the fastener tape disclosed in US Pat. No. 3,848,594 (Buell), issued 19 November 1974, incorporated by reference. obtain. Those tape tab fasteners or other diaper fastener means are typically applied near the corner of the diaper 60.
[0139]
The elastic member 69 is disposed adjacent to the periphery of the diaper 60 and preferably along the respective longitudinal edges 64 so that the elastic member abuts the wearer's leg to facilitate pulling and holding the diaper 60. . The elastic member 67 may also be disposed proximate to one or both of the waistband regions 63 of the diaper 60 to provide a waistband similar to or rather than the leg cuffs. For example, a suitable waistband is disclosed in US Pat. No. 4,515,595 (Kievit et al.) Issued May 7, 1985, incorporated by reference. Also, a suitable method and apparatus for manufacturing a disposable diaper having an elastically shrinkable elastic member is disclosed in U.S. Pat. No. 4,081,301 issued Mar. 28, 1978, which is incorporated by reference. Buell).
[0140]
The elastic member has an ordinary unrestrained shape and is fixed to the diaper 60 in an elastically contractible state so that the elastic member effectively contracts or gathers the diaper 60. The elastic member can be fixed in an elastically contractible state in at least two ways. For example, the elastic member can be stretched and secured while the diaper 60 is present in an uncontracted state. Alternatively, the diaper 60 can be contracted, for example by pleating, and the elastic member can be secured and connected to the diaper 60 while the elastic member is in its unrelaxed or unstretched state. The elastic member can extend along a portion of the length of the diaper 60. Alternatively, the elastic member may extend the entire length of the diaper 60 or any other length suitable to provide an elastically shrinkable line. The length of the elastic member is defined by the design of the diaper.
[0141]
In use, the diaper 60 places one waistband region under the wearer's back and the diaper 60 between the wearer's legs so that the other waistband region is placed over the front of the wearer. Wear the wearer by pulling the rest. A tape tab 65 or other fastener is then preferably secured to the area facing the outside of the diaper 60. In use, a disposable diaper or other absorbent product that includes the storage absorbent member of the present invention can more efficiently store liquid and remain dry due to the high absorbent capacity and high suction capacity of the absorbent member.
[0142]
When used as an absorbent core in a disposable diaper 60, a preferred embodiment of the core 28 according to the present invention is that the capture strip 52 is in fluid communication with the topsheet 61 to rapidly capture and absorb body exudates from the wearer's body. It is located to serve the distribution to the distribution strip 51. Adhesive bonding of the capture strip 52 to the topsheet 61 may provide interfacial bonding and enhance liquid communication by preventing topsheet separation from interfering with liquid flow. The dispensing material 51 moves the liquid in the x and y dimensions of the core 28 and is subsequently desorbed by a liquid storage element that is a storage absorbent member of the present invention, generally designated as 10. Although elements 52 and 51 are generally enclosed in straight lines and shown as being of equal size, other form and size relationships may be utilized. As shown, the generally rectilinear element has a width 53 that corresponds to an appropriate width for the crotch 66 of the disposable diaper. Similarly, the length of each core member may vary to provide a suitable fit for various wearer sizes.
[0143]
As shown in FIG. 1, the storage member 10 may have two separate storage absorbent members 20 and 30 such that there are no absorbent storage member elements located in the liquid discharge area of the diaper. Such a storage absorbent member 10 has little or no liquid storage material in the center of the core (corresponding to the crotch of the core or the liquid discharge area) (the dispensing material 51 may have a significant storage capacity. However, it should be recognized that it contains liquid until it is desorbed by at least a stronger suction storage material), so that a product containing such a core will have some load on the product when it is dry and on body fluids. It can provide better fit and wearer comfort both after receiving. For example, G. U.S. patent application Ser. No. 08 / 825,072 filed Mar. 27, 1997, by Young et al. US patent application Ser. No. 08 / 825,071, filed Mar. 27, 1997, by LaVon et al. See U.S. Patent Application Serial No. 08 / 826,208, filed March 27, 1997 by Young et al. FIG. 2a shows an exploded view of an absorbent core 28 having two separate elements 20 and 30, each of which comprises a storage absorbent member of the present invention. The front panel 20 generally corresponds to the portion of the disposable diaper worn in front of the wearer. Similarly, the back panel 30 corresponds to a disposable diaper portion worn behind the wearer.
[0144]
Alternatively, the storage absorbent member 10 can be an integral layer of the storage absorbent material of the present invention (i.e., the dotted line 70 in FIG. 1 indicates that the storage absorbent member 10 is included in the liquid discharge area of the product). If). Such an embodiment of the absorbent core 28 is depicted in FIG.
[0145]
In one embodiment, the capture strip 52 is a liquid treatment layer located in the liquid drain region of the product wearer in the form of a high loft nonwoven, but is preferably modified such as, for example, cured and curled cellulosic fibers. It is present in the form of a liquid acquisition layer comprising a layer of cellulose fibers and optionally up to about 10% by weight of this liquid acquisition / distribution layer of polymer gelling agent. In a preferred embodiment, the capture strip 52 is a cured and curled cellulosic fiber (eg, CMC® available from Weyerhauser Co., Washington; also Procter & Gamble Company, Paper Technology Division, Cincinnati, Ohio. High loft chemically bonded polyethylene terephthalate (PET) nonwoven layer (eg, about 42 g / m) overlying a layer of ² And a PET nonwoven layer is disposed between the cured and curled cellulosic fibers and the topsheet. The modified cellulosic fibers used in the liquid capture layer 52 of such preferred absorbent products are preferably wood pulp fibers that have been cured and curled by chemical and / or thermal treatment. Such modified cellulosic fibers are used in absorbent products as described in US Pat. No. 4,935,622 (Lash et al.) Issued June 19, 1990, incorporated by reference. Of the same type. A preferred embodiment is that the liquid distribution layer 51 is a co-pending T.P. A. US patent application Ser. No. 09 / 042,418 (P & G Case 7051) filed Mar. 13, 1998 by Desmalez, or co-pending G. As described in US patent application Ser. No. 08 / 633,630 filed Apr. 17, 1996 by Seger et al., Which are hereby incorporated by reference. [In a preferred embodiment utilizing a fibrous distribution material as described in co-pending U.S. patent application Ser. No. 08 / 633,630, the distribution material is each a raised or grooved perimeter (these are permanent webs). At least two rollers having a close gap) to undergo general deformation. A similar method has been developed for processing stretch laminate materials and is described by US Pat. No. 5,167,897 (Weber et al.) Regarding stretch materials. In essence, these methods provide mechanical processing of the web. The optional liquid distribution layer is typically located between and in fluid communication with the (upper) liquid treatment (eg, liquid capture material) and the (lower) high suction storage and absorption layer. An absorbent product that can utilize the storage absorbent member of the present invention in the lower liquid storage layer below the upper liquid capture / distribution layer containing cured and curled cellulosic fibers was issued on September 15, 1992. U.S. Pat. No. 5,147,345 (Young et al.).
[0146]
As referred to herein, a “disposable” absorbent product is intended to be discarded after a single use (ie, the original absorbent product as a whole is either washed or It is not intended to be repaired or reused as an absorbent product, however, certain materials or absorbent products can all be recycled, reused or composted). As used herein, the term “diaper” refers to a garment commonly worn by children and incontinent persons who are worn around the lower torso of the wearer. However, the present invention is also applicable to other absorbent products such as incontinence briefs, incontinence pads, training pants, diaper inserts, sanitary pads, sanitary napkins, tampons, bandages, facial tissues, paper towels, etc. Should be understood.
[0147]
VI. Test method
A. Capillary adsorption
the purpose
The purpose of this test is to measure the capillary absorption capacity of the storage absorbent member of the present invention as a function of height. (This test also shows the capillary adsorption capacity as a function of height for high surface area materials, i.e. materials that do not contain osmotic absorbents such as hydrogel-forming absorbent polymers or other optional materials utilized in absorbent members. Nonetheless, the following discussion discusses the capillary adsorption method to measure the entire storage absorbent member, where appropriate, as long as appropriate.) Capillary adsorption is where the liquid is absorbed into the absorbent structure. It is a basic property of any absorbent that governs how it is absorbed. In capillary adsorption experiments, the capillary adsorption capacity is measured as a function of liquid pressure as a function of sample height relative to the test fluid reservoir.
[0148]
Methods for measuring capillary adsorption are well known. Burgeni, AAand Kapur, C., “Capillary Sorption Equilibria in Fiber Masses”, Textile Research Journal, 37 (1967), 356-366; Chatterjee, PK, “Absorbency”, Textile Science and Technology 7, Chapter II, pp 29-84, Elsevier Science Publishers BV, 1985; and a US patent issued to Weisman et al. On September 9, 1986 for discussion of methods for measuring capillary adsorption of absorbent structures. See 4,610,678. The disclosure of each of these references is incorporated herein by reference.
[0149]
principle
A porous glass frit is connected through a continuous column of liquid to a liquid reservoir on the balance. During the experiment, the sample is kept under a constant containment weight. Since the porous structure absorbs liquid on demand, the weight loss in the scaled liquid reservoir is recorded as liquid uptake and adjusted for glass frit uptake as a function of height and evaporation. Take up or measure volume with various capillary aspirations (hydrostatic tension or height). Incremental absorption occurs because of the progressive decrease in frit (ie, the decrease in capillary suction).
[0150]
During the experiment, the time is also monitored so that the initial effective uptake rate (g / g / h) at a height of 200 cm can be calculated.
[0151]
reagent
Test solution: Synthetic urine is prepared by completely dissolving the following materials in distilled water.
[0152]
Compound F. W. Concentration (g / L)
KCl 74.6 2.0
Na ₂ SO _Four 142 2.0
(NH _Four ) H ₂ PO _Four 115 0.85
(NH4) ₂ HPO _Four 132 0.15
CaCl ₂ ・ 2H ₂ O 147 0.25
MgCl ₂ ・ 6H ₂ O 203 0.5.
[0153]
General description of equipment layout
The capillary adsorption test apparatus used for testing, generally indicated as 220 in FIG. 8A, is operated under TAPPI conditions (50% RH, 25 ° C.). The test sample is placed on a glass frit, shown as 202 in FIG. 8A, connected through a continuous column of test liquid (synthetic urine) to a scaled liquid reservoir, designated 206, containing the test liquid. Is done. This reservoir 206 is placed on a scale 207 connected to a computer (not shown). The scale must be able to read up to 0.001 g. Such a scale is available from Mettler Toledo (Heightstown, NJ) as PR1203. The glass frit 202 is placed on a vertical slide, generally indicated as 201 in FIG. 8A, to allow vertical movement of the test sample to expose the test sample to various suction heights. The vertical slide may be a rodless actuator connected to a computer to record the suction height and corresponding time to measure the amount of liquid uptake by the test sample. A preferred rodless actuator is available from Industrial Devices (Novato, Calif.) As model number 202X4X34N-1D4B-84-PCSE, which is a CompuMotor (Rohnert, Calif.). Can be powered by a motor drive ZETA 6104-83-135 available from the state). When data is measured and data is sent from the actuator 201 and the scale 207, capillary adsorption / absorption capacity data is easily generated for each test sample. Further, since the computer is connected to the actuator 201, the vertical movement of the glass frit 202 can be controlled. For example, the actuator can command the glass frit 202 to move vertically only after reaching “equilibrium” (defined below) at each suction height.
[0154]
The bottom of the glass frit 202 is connected to a Tygon (registered trademark) tube that connects the frit 205 to a drain three-way stopcock 209. The drain stopcock 209 is connected to the liquid reservoir 205 via the glass tube 204 and the stopcock 210. (The stopcock 209 is opened toward the drain only during cleaning of the apparatus or during the removal of bubbles.) The glass tube 211 connects the liquid reservoir 205 and the scaled liquid reservoir 206 via the stopcock 210. . The liquid reservoir with scale 206 is composed of a lightweight 12 cm diameter glass pan 206A and a cover 206B. Cover 206B has a hole through which glass tube 211 contacts the liquid in reservoir 206. The glass tube 211 must not touch the cover 206B, otherwise it will cause an unstable scale reading and test sample measurements will not be available.
[0155]
The glass frit diameter must be sufficient to fit the piston / cylinder apparatus described below to hold the test sample. The glass frit 202 is provided with a jacket so that a constant temperature control from the heating bath can be performed. The frit is a 350 mL frit glass disc funnel defined as having 4 to 5.5 μm pores and is available as # 36060-350F from Corning Glass Co. (Corning, NY). The pores are fine enough to keep the frit surface wet at a defined capillary suction height (the glass frit does not allow air to enter the continuous column of test liquid below the glass frit).
[0156]
As described above, the frit 202 is connected to the liquid reservoir 205 or the liquid reservoir 206 with a scale via a tube according to the position of the three-way stopcock 210.
[0157]
The glass frit 202 is provided with a jacket for receiving water from the thermostatic bath. This will ensure that the glass frit temperature is maintained at a constant temperature of 88 ° F. (31 ° C.) during the test procedure. As shown in FIG. 8A, the glass frit 202 is provided with an inlet port 202A and an outlet port 202B, which form a closed loop with a circulating heating bath, generally designated 208. (A glass jacket is not shown in FIG. 8A. However, the water introduced from the bath 208 to the jacketed glass frit 202 does not contact the test solution, and the test solution circulates through the thermostatic bath.) (The water in the thermostat circulates through the jacket wall of the glass frit 202.)
Reservoir 206 and scale 207 are encased in a box to minimize test solution evaporation from the scaled reservoir and to enhance the stability of the scale during the course of the experiment. This box, generally designated 212, has an upper lid and a wall with a hole through which the tube 211 is inserted.
[0158]
The glass frit 202 is shown in more detail in FIG. 8B. FIG. 8B is a cross-sectional view of the glass frit shown without inlet port 202A and outlet port 202B. As mentioned above, the glass frit is a 350 mL fritted glass circular funnel with defined 4-5.5 μm pores. Referring to FIG. 8B, the glass frit 202 has a cylindrical jacketed funnel shown as 220 and a glass frit disc shown as 260. In addition, the glass frit 202 has a cylinder / piston assembly (comprising a cylinder 266 and piston 268), generally designated as 265, that encloses the test sample, designated as 270, and is small in the test sample. Give confinement pressure. In order to prevent excessive evaporation of the test liquid from the glass frit disc 260, a Teflon ring, designated as 262, is placed on top of the glass frit disc 260. The Teflon ring 262 is 0.0127 cm thick (available as seat stock as # 8569K16 from McMasterCarr and cut to the appropriate size) and the frit outside the cylinder 266 Used to coat the disk surface, thus minimizing evaporation from the glass frit. The outer diameter and inner diameter of the ring are 7.6 and 6.3 cm, respectively. The inner diameter of the Teflon ring 262 is about 2 mm smaller than the outer diameter of the cylinder 266. Viton® O-ring (available as # AS568A-150 and AS568A-151 from McMasterCarr) 264 further enhances the inner wall of the cylindrical jacketed funnel 250 and Teflon (registered) to help prevent evaporation The Teflon ring 262 is placed on top of the Teflon ring 262 to seal the gap between it and the trademark ring 262. If the outer diameter of the O-ring is larger than the inner diameter of the cylindrical jacketed funnel 250, reduce the O-ring diameter to fit the funnel as follows. The O-ring is cut open and the required amount of O-ring material is cut and pasted again so that the O-ring contacts the inner wall of the cylindrical jacketed funnel 250 at its entire circumference.
[0159]
As noted above, the cylinder / piston assembly, generally shown as 265 in FIG. 8B, confines the test sample and provides a small confinement pressure to the test sample 270. Referring to FIG. 8C, assembly 265 includes a cup-shaped Teflon piston indicated by cylinders 266, 268, and one or more weights (not shown) that fit inner piston 268 if necessary. Consists of (The optional weight is used when necessary to adjust the total weight of the piston and optional weight so that a confining pressure of 0.2 psi is achieved, depending on the dry diameter of the test sample. Wax, which is described below.) Cylinder 266 is a Lexan® bar stock and has the following dimensions: 7.0 cm outer diameter, 6.0 cm inner diameter and 6.0 cm height. Teflon piston 268 has the following dimensions: an outer diameter that is 0.02 cm smaller than the inner diameter of cylinder 266. As shown in FIG. 8D, the end of the piston 268 that does not contact the test sample has an optional weight required to achieve a test sample confinement pressure of 0.2 psi (1.4 kpa) (test sample). Is pierced to give a chamber 290 that is 5.0 cm diameter x about 1.8 cm deep. In other words, the total weight of the piston 268 and any optional weight (not shown) divided by the actual diameter of the test sample (when dry) achieves a 0.2 psi containment pressure. Must be like that. Cylinder 266 and piston 268 (and optional weight) are allowed to equilibrate for at least 30 minutes at 31 ° C. before performing capillary adsorption capacity measurements.
[0160]
During capillary adsorption experiments, a perforated film (14 cm × 14 cm) that has not been treated with surfactant or incorporated with surfactant to minimize air destabilization around the sample (Fig. (Not shown) is used to cover the glass frit 202. The holes are large enough to prevent condensation from occurring on the lower surface of the film during the experiment.
[0161]
Test sample preparation
The test sample can be obtained by punching out a 5.4 cm diameter circular structure from the storage absorbent member using an arch punch. If this member is an element of an absorbent product, the other elements of the product must be removed before testing. The member cannot be separated from other elements of the product without significantly changing its structure (eg density, relative placement of element materials, physical properties of the constituent materials, etc.) or the element is not an element of the absorbent product In the situation, the test sample is prepared by combining all the materials that make up the member such that the combination is a sample of the member in question.
[0162]
The dry weight of the test sample (used below to calculate the capillary adsorption capacity) is the weight of the test sample prepared under ambient conditions as described above.
[0163]
Preparation for experiment
1. A clean, dry glass frit 202 is placed on the funnel holder attached to the vertical slide 201. The vertical slide funnel holder is moved so that the glass frit is at a height of 0 cm.
[0164]
2. As described above, the device parts are set up as shown in FIG. 8A.
[0165]
3. Place a scaled liquid reservoir 206 on a scale 207 with a 12 cm diameter. A plastic lid 206B is placed over the scaled liquid reservoir 206, and the balance box 212 is covered with a plastic lid, each of which has a small hole to allow the glass tube 211 to fit through. The glass tube must not be in contact with the scaled liquid reservoir lid 206B, otherwise it will result in an unstable scale reading and the measurements will not be available.
[0166]
4). The stopcock 210 is closed with respect to the tube 204 and opened with respect to the glass tube 211. The liquid reservoir 205 filled with the test liquid in advance is opened, the test liquid is allowed to flow into the tube 211, and the liquid reservoir 206 with a scale is filled.
[0167]
5). The glass frit 202 is leveled and fixed in place. Also ensure that the glass frit is dry.
[0168]
6). A Tygon (registered trademark) tube 203 is attached to the stopcock 209. (The tube must be long enough to reach the glass frit 202 at the highest point of 200 cm without kinking.) Fill this Tygon® tube with test fluid from the liquid reservoir 205.
[0169]
7). After the Tygon (registered trademark) tube 203 is attached to the horizontal glass frit 202, the stopcock 209 and the stopcock 210 leading from the liquid reservoir 205 to the glass frit 202 are opened. (The stopcock 210 must be closed with respect to the glass tube 211.) Fill the glass frit 202 with the test solution and remove all trapped air during the horizontal glass frit filling. Continue filling until the liquid level exceeds the top of the glass frit disc 260. Empty the funnel and remove all air bubbles in the tube and inside the funnel. The bubbles can be removed by inverting the glass frit 202 and raising the bubbles to escape through the drain of the stopcock 209. (Typically, air bubbles collect on the bottom of the glass frit disc 260.) Level the frit again using a level small enough to fit inside the jacketed funnel 250 and on the surface of the glass frit disc 260. To.
[0170]
8). The glass frit is zeroed by the scaled liquid reservoir 206. To do this, take a single Tygon® tube of sufficient length and fill it with the test solution. One end is placed in the scaled liquid reservoir 206 and the other end is used to place the glass frit 202. The level of test fluid indicated by the tube (same as the level of the scaled fluid reservoir) is 10 mm below the top of the glass frit disc 260. If not, adjust the amount of liquid in the reservoir or reset the zero position on the vertical slide 201.
[0171]
9. The outlet port and inlet port from the thermostat 208 are attached to the glass frit inlet port and outlet ports 202A and 202B via tubes, respectively. The temperature of the glass frit disk 260 is set to 31 ° C. This can be measured by partially filling the glass frit with the test liquid and measuring the temperature after it reaches the equilibrium temperature. In order to allow heat dissipation during the transfer of water from the vessel to the glass frit, the vessel would need to be set to a temperature somewhat above 31 ° C.
[0172]
10. Allow the glass frit to equilibrate for 30 minutes.
[0173]
Capillary adsorption parameters
The following describes a computer program that measures how long a glass frit stays at each height.
[0174]
In the capillary adsorption test software program, the test sample is at a certain height from the liquid reservoir. As described above, the liquid reservoir is above the scale so that the computer can read the scale at the end of the known time interval and calculate the flow rate between the test sample and the reservoir (delta reading / time interval). is there. Because of this method, a test sample is considered to be in equilibrium when the flow rate is less than the specified flow rate for a specified number of consecutive time intervals. It is recognized that for certain materials, the actual equilibrium may not be reached when the prescribed “equilibrium constant” is reached. The time interval between readings is 5 seconds.
[0175]
The number of readings in the delta table is defined as “equilibrium sample” in the capillary adsorption menu. The maximum number of deltas is 500. The flow rate constant is defined as “equilibrium constant” in the capillary adsorption menu.
[0176]
The equilibrium constant is input in the range of 0.0001 to 100,000 in units of g / sec.
[0177]
The following is a simplified example of logic. The table shows the scale readings and the calculated delta flow for each time interval.
[0178]
Equilibrium sample = 3
Equilibrium constant =. 0015
[Table 1]

[0179]
[Table 2]

[0180]
[Table 3]

[0181]
The equilibrium uptake for the simplified example above is 0.318 g.
Below is the C language code used to determine the equilibrium uptake.
[0182]
[Table 4]

[0183]
Capillary adsorption parameters
Load description (confinement pressure): 0.2 psi load
Equilibrium sample (n): 50
Equilibrium constant: 0.0005 g / sec
Setup height value: 100cm
Final height value: 0cm
Hydrostatic head parameters: 200, 180, 160, 140, 120, 100, 90, 80, 70, 60, 50, 45, 40, 35, 30, 25, 20, 15, 10, 5 and 0 cm
For the measurement of the capillary adsorption capacity, the capillary adsorption test procedure is carried out using all the heights defined above in the order described above. Even if it is desirable to measure capillary adsorption capacity at a particular height (eg 35 cm), the entire series of hydrostatic head parameters must be completed in a prescribed order. Although all of these heights are used in the performance of a capillary adsorption test to generate a capillary adsorption isotherm for a test sample, the present disclosure discloses specific heights of 200, 140, 100, 50, 35 and 0 cm. The storage absorbent member will be described on the basis of their absorption characteristics.
[0184]
Capillary adsorption test procedure
1) Follow the experimental preparation procedure.
[0185]
2) Check that the thermostat 208 is on, water is circulating through the glass frit 202, and the temperature of the glass frit disc 260 is 31 ° C.
[0186]
3) Place the glass frit 202 at a suction height of 200 cm. Stopcocks 209 and 210 are opened to connect glass frit 202 to scaled liquid reservoir 206 (stopcock 210 closes against liquid reservoir 205). Glass frit 202 is allowed to equilibrate for 30 minutes.
[0187]
4) Input the above capillary adsorption parameters into the computer.
[0188]
5) Close stopcocks 209 and 210.
[0189]
6) Move the glass frit 202 to a setup height of 100 cm.
[0190]
7) Place the Teflon ring 262 on the surface of the glass frit disk 260. Place the O-ring 264 on the Teflon ring. A preheated cylinder 266 is placed concentrically on the Teflon ring. A test sample 270 is placed concentrically on a cylinder 266 on a glass frit disk 260. The piston 268 is placed in the cylinder 266. If necessary, an additional containment weight is placed in the piston chamber 290.
[0191]
8) Cover glass frit 202 with perforated film.
[0192]
9) Confirm that the scale reading at this point is zero or the dead weight reading.
[0193]
10) Move the glass frit 202 to 200 cm.
[0194]
11) Open stopcocks 209 and 210 (stopcock 210 is closed to liquid reservoir 205) and begin reading scale and time.
[0195]
Glass frit correction (Blank correction loading)
Since the glass frit disk 260 is a porous structure, it must be subtracted to measure the capillary adsorption / absorption uptake (blank corrected uptake) of the glass frit (202) and to obtain the capillary adsorption / absorption uptake of the true test sample. I must. Glass frit correction is performed for each new glass frit used. A capillary adsorption test procedure is performed as described above except that no test sample is used to obtain a blank uptake (g). The elapsed time at each specified height is equal to the blank time (s).
[0196]
Evaporation loss correction
1) Move glass frit 202 2 cm above zero and open stopcocks 209 and 210 (closed to reservoir 205) and allow it to equilibrate at this height for 30 minutes.
[0197]
2) Close stopcocks 209 and 210.
[0198]
3) Place a Teflon ring 262 on the surface of the glass frit disk 260. Place the O-ring 264 on the Teflon ring. A preheated cylinder 266 is placed concentrically on the Teflon ring. The piston 268 is placed in the cylinder 266. A perforated film is placed on the glass frit 202.
[0199]
4) Open stopcocks 209 and 210 (closed to reservoir 205) and record scale reading and time over 3.5 hours. The sample evaporation (g / hr) is calculated as follows.
[0200]
[Scale reading in 1 hour-Scale reading in 3.5 hours] /2.5 hours
Even after taking all of the above precautions, some evaporation loss, typically about 0.10 g / hr evaporation loss will occur for both the test sample and frit correction. Ideally, sample evaporation is measured for each newly installed glass frit 202.
[0201]
Cleaning the equipment
When the glass frit 202 is newly installed, a new Tygon (registered trademark) tube 203 is used. Glass tubes 204 and 211, liquid reserve 205, and scaled liquid reservoir 206 are rinsed with distilled water after washing with 50% Clorox Bleach® / distilled water if bacterial contamination is visible Wash.
[0202]
a. Cleaning after each experiment
At the end of each experiment (after removing the test sample), the glass frit is flushed forward (ie, the test liquid is introduced into the bottom of the glass frit) with 250 mL of test liquid from the liquid reservoir 205 to obtain a glass frit disk. Remove the residual test sample from the holes. Stopcocks 209 and 210 are opened to the liquid reservoir 205, closed to the scaled liquid reservoir 206, the glass frit is removed from its support, turned upside down and first rinsed with the test solution, then acetone. And rinse with test solution. During rinsing, the glass frit must be tilted upside down and the rinsing liquid is jetted onto the test sample contact surface of the glass frit disk. After rinsing, the glass frit is flushed twice with 250 mL synthetic urine. Finally, reattach the glass frit to the support and level the frit surface.
[0203]
b. Glass frit performance monitor
The performance of the glass frit must be monitored with a glass frit setup at the 0 cm position after each cleaning procedure and each time a new glass frit is installed. Pour 50 mL of test fluid onto a leveled glass frit disk surface (without Teflon ring, O-ring and cylinder / piston parts). Record the time required for the test solution level to drop 5 mm above the glass frit disk surface. If this time exceeds 4.5 minutes, periodic cleaning must be performed.
[0204]
c. Regular cleaning
Periodically (see frit performance monitor above) clean glass frit thoroughly to prevent clogging. The rinse is distilled water, acetone, 50% Clorox Bleach® / distilled water (to remove bacterial growth) and test solution. Cleaning includes removing the glass frit from the support and removing all tubes. Turn the frit upside down and with the appropriate liquid and amount, forward flush the glass frit in the following order (ie, introduce the test solution to the bottom of the glass frit).
[0205]
1. 250 mL distilled water
2. 100 mL of acetone
3. 250 mL distilled water
4. 100 mL of 50:50 Clorox® / distilled aqueous solution
5. 250 mL distilled water
6. 250 mL test solution
If the performance of the glass frit is within the flow rate setting criteria (see above) and no residue can be observed on the glass frit disc surface, the cleaning procedure is satisfactory. If cleaning is not successful, the frit must be changed.
[0206]
Calculation
The computer is set up to give a report consisting of capillary suction height (cm), time, and uptake (grams) at each specified height. From this data, the capillary suction absorption capacity corrected for both frit uptake and evaporation loss can be calculated. Moreover, based on the capillary suction absorption capacity at 0 cm, the capillary absorption efficiency at the specified height can be calculated. In addition, the initial effective uptake rate at 200 cm is calculated.
[0207]
Blank correction capture amount
Blank correction uptake amount (g) = Blank uptake amount (g) −Blank time * Sample evaporation amount (g / hr) / 3600 (s / hr)
Capillary suction adsorption capacity (“CSAC”):
CSAC (g / g) = {sample uptake (g) − (sample time * sample evaporation (g / hr) / 3600 (s / hr)) − blank corrected uptake (g)} / dry weight of sample ( g)
Initial effective uptake rate at 200cm ("IEUR")
IEUR (g / g / hr) = Sample time (s) at CSAC (g / g) / 200 cm at 200 cm.
[0208]
Report
In order to calculate the capillary absorption capacity for a given absorbent member or a given large surface area material, a minimum of two measurements must be taken for each sample and the uptake must be averaged at each height.
[0209]
B. Vertical hanging suction height (VHSH)
A vertical suspended adsorption height (“VHSH”) test is achieved by selecting a strip of foam of a suitable length (typically at least 60 cm) and typically a width of about 1 cm. Using a clip to suspend the strip, suspend the strip in a chamber temperature controlled at 31 ° C. The bottom of the strip is immersed in the 31 ° C. test solution. The test solution is preferably synthetic urine as described in US Pat. No. 5,599,335 (Goldman et al.), Issued February 4, 1997, the disclosure of which is incorporated herein by reference. . Over time, the test solution will suck up the strip and reach an equilibrium point where no further suction will occur. In order to facilitate the determination of the equilibrium point, the test solution may be dried. For example, care must be taken to prevent evaporation from the sample by placing the sample in a glass tube (glass does not contact the sample) and keeping the sample tube properly capped. The time required to reach equilibrium for the materials of the present invention can vary and ranges from about 24 hours to 96 hours or more. Equilibrium is considered achieved if there is no discernable change in the level of wicking liquid over an hour.
[0210]
Remove the test strip from the test chamber, taking care to avoid squeezing out the liquid retained therein. A plurality of sections 2.5 cm in length are cut from the strip and each section is weighed. For convenience, an initial section that is about 50% or less of the fully expanded height may be cut into 2 inch (5.1 cm) long sections. These weights are divided by the oven dry weight of the foam to calculate the capacity (g / g) of the foam at various multivalent s. By graphing a capacity chart with respect to the height at which a section is collected, a graph as shown in FIG. 5 can be developed. The VHSH height at X% is the height (cm) when 0% capacity (or FAC) X% is retained in the foam. An important representative value is VHSH at 90%. In principle, X can be any value. The most reproducible measurement for VHSH is achieved at X = 90% within the inventors' experience. It will be apparent to those skilled in the art that the numerical value at this point does not adequately represent the shape of the curve obtained by plotting capacity against height. However, this one point serves as a practical comparison point for the foams of the present invention.
[0211]
【Example】
VII. Representative example
Example 1
Storage / absorbing member containing ultrafine glass fiber
In this example, a high gel containing hydrogel-forming absorbent polymer and high surface area glass ultrafine fibers formed using a wet end molding process for higher density and structural organization than conventional air deposition processes. The capillary suction absorbing member will be described. The following procedure is followed to construct a member containing a hydrogel-forming absorbent polymer such that the distribution of the absorbent polymer in the glass microfiber matrix is close to homogeneous.
[0212]
4.0 g of ASAP 2300 (available from Chemdal LTD, a subsidiary of American Colloid Co. of Arlington Heights, Ill .; and The Procter & Gambling, Inc. Also available from the Paper Technology Division of Gamble CO.) And 4.0 g of glass microfiber (from “Q-FIBERS,” code from Manville Sales Corp., Denver, Colorado) Degrading the structure or composition of about 500 mL of 3A alcohol (95% ethanol, 5% methanol), or isopropanol or similar liquid (contained polymers) And is not absorbed into it), and the explosion-proof capacity of 3 gallons Grade of Warner (Warner) is bound in a blender. Of the included hydrogel Structure Or composition If the liquid is not absorbed by Such a liquid include Hydrogel-forming absorbent polymer 1 gram About 5 grams per liquid (about 5g / g by weight) Less than a small range so Structure Or it is only absorbed into the composition. Stir the mixture at low speed for about 5 minutes. The mixture is equipped with an 80 mesh nylon forming wire (available from Appleton Manufacturing Division of Productive Solutions, Inc., Nina, Wyoming) at the bottom of the upper portion of the paper box. It is poured into a 6 inch x 6 inch "Paper Formation Box". The liquid level is about 8 inches above the screen with the addition of 3A alcohol or a suitable solution. Prior to draining the liquid, thoroughly mix the solution at the top of the paper box using a paddle. The valve is opened below the forming wire to quickly drain the liquid and ensure uniform deposition on the forming wire. The screen is removed from the “paper box” and pulled across the vacuum source to remove loosely held liquid and desiccant (eg, DRIERITE, Sigme Chem. Co., 63178, St. Louis, MO). Air-dry overnight in a desiccator containing to ensure uniform moisture content. Once dried, the absorbent member is removed from the molding screen.
[0213]
An 5.4 cm cylindrical structure is arch punched from this member for measurement of capillary adsorption capacity. The capillary adsorption isotherm of this storage absorbent member is illustrated graphically in FIG.
[0214]
Example 2
Preparation of high surface area foam from HIPE
A) Preparation of HIPE
Anhydrous calcium chloride (36.32 kg) and potassium persulfate (189 g) are dissolved in 378 liters of water. This provides an aqueous phase stream that is used in a continuous process to form a HIPE emulsion.
[0215]
A diglycerol monooleate emulsifier is added to a monomer mixture comprising distilled divinylbenzene (42.4% divinylbenzene and 57.6% ethylstyrene) (2640 g), 2-ethylhexyl acrylate (4400 g), and hexanediol diacrylate (960 g). (480 g), ditallow dimethyl ammonium methyl sulfate (80 g), and Tinuvin 765 (20 g) are added. Diglycerol monooleate emulsifier (Grindsted Products; Brabrand, Denmark) is about 81% diglycerol monooleate, 1% other diglycerol monoesters, 3% polyol And 15% of other polyglycerol esters, giving a minimum oil / water interfacial tension value of about 2.7 dyne / cm and having an oil / water critical coagulation concentration of about 2.8% by weight. After mixing, the material mixture is allowed to stand overnight. No visible residue is formed and the entire mixture is removed and used as the oil phase in a continuous process to form a HIPE emulsion.
[0216]
Separate streams of oil phase (25 ° C) and aqueous phase (53-55 ° C) are fed to the dynamic mixing device. Complete mixing of the combined flows in the dynamic mixing device is achieved by a pin impeller. The pin impeller has a cylindrical shaft about 36.5 cm long and about 2.9 cm in diameter. The shaft holds 6 rows of pins, 3 rows have 33 pins and 3 rows have 34 pins, each 3 pins of each level being arranged at an angle of 120 ° to each other, The next lower level is positioned at 60 ° to the adjacent level, with each level separated by 0.03 mm, and each pin has a diameter of 0.5 cm and a length of 2.3 cm from the central axis of the shaft. Now it ’s going out. The pin impeller is attached to a cylindrical sleeve forming a dynamic mixing device, and the pin has a spacing of 1.5 mm from the wall of the cylindrical sleeve.
[0217]
As shown in the figure in copending US patent application Ser. No. 08 / 716,510 filed by DesMarais on Sep. 17, 1996, the disclosure of which is incorporated herein by reference. A small portion of the effluent coming out of the dynamic mixing device is collected and flows into the recirculation zone. The Waukesha pump in the recirculation zone returns this small portion to the oil and water phase flow entry points to the dynamic mixing zone.
[0218]
The static mixer (TAH Industries model 100-812) has 12 elements with an outer diameter of 1 inch (2.5 cm). A hose is attached downstream from the static mixer to facilitate the feeding of the emulsion to the equipment used for curing. Optionally, use an additional static mixer to provide additional back pressure so that the hose continues to fill. The optional static mixer may be a 1 inch (2.5 cm) pipe, 12 element mixer (McMaster-Carr, Aurora, Ohio, model 3529K53).
[0219]
A combined mixed recirculator mechanism is filled with an oil phase and an aqueous phase at a ratio of 4 parts water to 1 part oil. The dynamic mixing device is evacuated to allow air to escape while the device is completely filled. The flow rate during filling is 7.57 g / sec for the oil phase and 30.3 cc / sec for the water phase.
[0220]
When the device mechanism is filled, the impeller is rotated at 1750 RPM and stirring is started with a dynamic mixer, and recirculation is started at a speed of about 30 cc / sec. Thereafter, the flow rate of the aqueous phase is gradually increased to 151.3 cc / sec over about 1 minute, and the flow rate of the oil phase is decreased to 3.03 g / sec over about 3 minutes. The recirculation rate is gradually increased to about 150 cc / sec during the latter time. The back pressure created by the dynamic zone and static mixer at this point is about 19.9 PSI (137 kPa), which represents the total pressure drop of the system. Thereafter, the speed of the Waukesha pump (model 30) is gradually reduced to produce a recirculation rate of about 75 cc / sec.
[0221]
B) Polymerization of HIPE
The flow of HIPE from the static mixer at this point was 40 inches (102 cm) in diameter and 12.5 inches in height (31. 8 cm) round polyethylene tabs. A pipe-shaped polyethylene insert with a diameter of 12.5 inches (31.8 cm) at the bottom is firmly fixed to the center of the bottom surface and has a height of 12.5 inches (31.8 cm). The HIPE-containing tub is maintained for 18 hours in a room maintained at 65 ° C. and polymerizes to form a foam.
[0222]
C) Foam cleaning and moisture removal
The cured HIPE foam is removed from the curing tab. The foam at this point has a residual aqueous phase (including dissolved emulsifier, electrolyte, initiator residue and initiator) of about 48 to 52 times (48 to 52 ×) the weight of polymerized monomer. The foam is sliced into 0.185 inch (4.7 mm) thick sheets by a sharp reciprocating saw blade. These sheets are then compressed to about 6 times the weight of the polymerized material (6 ×) by a series of two porous nip rolls equipped with a vacuum that gradually reduces the residual aqueous phase content of the foam. . At this point, the sheet is further 1.5% CaCl at 60 ° C. ₂ It is re-saturated with the solution and squeezed to a water phase content of about 4 times by a series of three porous nip rolls equipped with vacuum. Foam CaCl ₂ The content is 8-10%.
[0223]
The foam remains compressed to a thickness of about 0.021 inches (0.053 cm) after the final nip. The foam is then air dried for about 16 hours. Such drying reduces the water content to about 9-17%, based on the weight of the polymeric material. At this point, the foam sheet is extremely draped and is “thin-after-drying”.
[0224]
Example 3
Preparation of high surface area foam from HIPE
A) Preparation of HIPE
The aqueous and oil phase streams used in the continuous process to form the HIPE emulsion are prepared according to Example 1. Separate streams of oil phase (25 ° C.) and aqueous phase (53-55 ° C.) are fed to the dynamic mixing apparatus detailed in Example 1.
[0225]
Once the device mechanism is filled, the impeller is rotated at 1700 RPM to start stirring with the dynamic mixer and recirculation is started at a rate of about 30 cc / sec. Thereafter, the flow rate of the aqueous phase is gradually increased to 151.3 cc / sec over about 1 minute, and the flow rate of the oil phase is decreased to 3.36 g / sec over about 3 minutes. The recirculation rate is gradually increased to about 150 cc / sec during the latter time. The back pressure created by the dynamic zone and static mixer at this point is about 19.7 PSI (136 kPa), which represents the total pressure drop of the system. Thereafter, the speed of the Waukesha pump is gradually reduced, resulting in a recirculation rate of about 75 cc / sec.
[0226]
B) Polymerization of HIPE
At this point, the HIPE flowing from the static mixer is collected and cured into a polymer foam as detailed in Example 1.
[0227]
C) Foam cleaning and moisture removal
The cured HIPE foam is removed from the curing tab. The foam at this point has a residual aqueous phase (including dissolved emulsifier, electrolyte, initiator residue and initiator) of about 43 to 47 times (43 to 47 ×) the weight of polymerized monomer. The foam is sliced into 0.185 inch (4.7 mm) thick sheets by a sharp reciprocating saw blade. These sheets are then compressed to about 6 times the weight of the polymerized material (6 ×) by a series of two porous nip rolls equipped with a vacuum that gradually reduces the residual aqueous phase content of the foam. . At this point, the sheet is further 1.5% CaCl at 60 ° C. ₂ It is re-saturated with the solution and squeezed to a water phase content of about 4 times by a series of three porous nip rolls equipped with vacuum. Foam CaCl ₂ The content is 8-10%.
[0228]
The foam remains compressed to a thickness of about 0.028 inches (0.071 cm) after the final nip. The foam is then air dried for about 16 hours. Such drying reduces the water content to about 9-17%, based on the weight of the polymeric material. At this point, the foam sheet can be very draped and is “thin-after-drying”.
[0229]
Example 4
Preparation of high surface area foam from HIPE
A) Preparation of HIPE
The aqueous and oil phase streams used in the continuous process to form the HIPE emulsion are prepared according to Example 1. Separate streams of oil phase (25 ° C.) and aqueous phase (53-55 ° C.) are fed to the dynamic mixing apparatus detailed in Example 1.
[0230]
Once the device mechanism is filled, the impeller is rotated at 1750 RPM to start stirring with the dynamic mixer and recirculation is started at a rate of about 30 cc / sec. Thereafter, the flow rate of the aqueous phase is gradually increased to 151.3 cc / sec over about 1 minute, and the flow rate of the oil phase is further decreased to 3.78 g / sec over about 3 minutes. The recirculation rate is gradually increased to about 150 cc / sec during the latter time. At this point, the back pressure created by the dynamic zone and static mixer is about 18.7 PSI (129 kPa), which represents the total pressure drop of the system. Thereafter, the speed of the Waukesha pump is gradually reduced, resulting in a recirculation rate of about 75 cc / sec.
[0231]
B) Polymerization of HIPE
At this point, the HIPE flowing from the static mixer is collected and cured into a polymer foam as detailed in Example 1.
[0232]
C) Foam cleaning and moisture removal
The cured HIPE foam is removed from the curing tab. The foam at this point has a residual aqueous phase (including dissolved emulsifier, electrolyte, initiator residue and initiator) that is approximately 38-42 times (38-42 ×) the weight of polymerized monomer. The foam is sliced into 0.185 inch (4.7 mm) thick sheets by a sharp reciprocating saw blade. These sheets are then compressed to about 6 times the weight of the polymerized material (6 ×) by a series of two porous nip rolls equipped with a vacuum that gradually reduces the residual aqueous phase content of the foam. . At this point, the sheet is further 1.5% CaCl at 60 ° C. ₂ The solution is re-saturated and squeezed by a series of three porous nip rolls equipped with vacuum to an aqueous phase content of about 4 times. Foam CaCl ₂ The content is 8-10%.
[0233]
The foam remains compressed to a thickness of about 0.028 inches (0.071 cm) after the final nip. The foam is then air dried for about 16 hours. Such drying reduces the water content to about 9-17%, based on the weight of the polymeric material. At this point, the foam sheet can be very draped and is “thin-after-drying”.
[0234]
Example 5
Storage absorbent member comprising a high surface area polymer foam material
This example describes a high capillary suction absorbent member comprising a hydrogel-forming absorbent polymer and a high suction polymer foam prepared according to Example 3. In order to construct a member containing a hydrogel-forming absorbent polymer in which the distribution of absorbent polymer and polymer foam is relatively close to homogeneity, the following procedure is followed.
[0235]
10 g of air-dried polymer foam (prepared according to Example 3 above) was added to a blender (Osterizer model 848-36L with a 1.25 liter jar containing 1 liter of 2% calcium chloride solution. ). After ensuring that all of the foam material is immersed, the blender is agitated for 10 seconds at “liquefaction” (high setting) and then further agitated for 5 seconds at the “Grate” setting. The resulting slurry is then transferred to a Buchner funnel (Coors USA model 60283) lined with paper towels. About 500 mL of liquid is drained free from the sample. The sample is then covered with a rubber membrane and subjected to vacuum (about 500 mmHg) to remove water from the sample to a weight of 50-60 g.
[0236]
The sample is returned to the dry blender jar and dispersed by agitation set to “liquefaction” while the jar and base are inverted several times to bring the sample into nearly independent particles and reversed upright. The dispersed samples are then allowed to air dry under ambient conditions before foam particles are available from a hydrogel-forming absorbent polymer (ASAP 2300, Chemdal Corporation, Parantine, Ill .; also the Cincinnati, Ohio • Combined with the Procter & Gamble CO. Paper Technology Division) and from a homogeneous mixture of 50% hydrogel-forming polymer by weight and 50% high surface area polymer foam by weight A storage absorbent member is provided.
[0237]
The capillary adsorption isotherm of this storage absorbent member is illustrated graphically in FIG.
[0238]
Example 6 Storage Absorbing Member Containing Large Surface Area Fibrets
In this example, a highly capillary suction absorbent member comprising a hydrogel-forming absorbent polymer and a large surface area fibrets is described. High surface area fibrets available from Hoechst Celanese Cop. (Charlotte, NC) as cellulose acetate fibrets® were converted to hydrogel-forming absorbent polymers (ASAP 2300, Chemdal Corporation, Parantine, Ill.). In combination with the paper technology division of The Procter & Gamble CO., Cincinnati, Ohio) and 50% by weight hydrogel-forming polymer and A storage absorbent member consisting of a homogeneous mixture of 50% fibrets by weight is provided.
[0239]
The capillary adsorption isotherm of this storage absorbent member is illustrated graphically in FIG.
[0240]
Example 7
Storage absorbent member comprising a high surface area polymer foam material
This example describes a high capillary suction absorbent member comprising a hydrogel-forming absorbent polymer and a high suction polymer foam prepared according to Example 3. In order to construct a member containing a hydrogel-forming absorbent polymer in which the distribution of absorbent polymer and polymer foam is relatively close to homogeneity, the following procedure is followed.
[0241]
10 g of air-dried polymer foam (prepared according to Example 3 above) was added to a blender (Osterizer model 848-36L with a 1.25 liter jar containing 1 liter of 2% calcium chloride solution. ). After ensuring that all of the foam material is immersed, the blender is agitated for 10 seconds at “liquefaction” (high setting) and then further agitated for 5 seconds at the “Grate” setting. The resulting slurry is then transferred to a Buchner funnel (Coors USA model 60283) lined with paper towels. About 500 mL of liquid is drained free from the sample. The sample is then covered with a rubber membrane and subjected to vacuum (about 500 mmHg) to remove water from the sample to a weight of 50-60 g.
[0242]
The sample is returned to the dry blender jar and dispersed by agitation set to “liquefaction” while the jar and base are inverted several times to bring the sample into nearly independent particles and reversed upright. The dispersed sample is then allowed to air dry under ambient conditions before the foam particles are combined with a mixed bed ion exchange hydrogel-forming absorbent polymer (described below) and 60% by weight of the hydrogel-forming polymer and A storage absorbent member consisting of a homogeneous mixture of 40% by weight high surface area polymer foam is provided.
[0243]
A) Preparation of mixed bed ion exchange absorbent polymer
(I) Preparation of Cation Exchange Absorbing Polymer-Crosslinked Polyacrylic Acid
Homogeneous crosslinked polyacrylic acid is synthesized by placing 450 grams of acrylic acid monomer (Aldrich Chemical Company, catalog number 14,723-0, lot number 15930CS) into a clean 4000 mL resin kettle. 7.2 grams of N, N′-methylenebisacrylamide (Aldrich Chemical Company, catalog number 14,607-2, lot number 04511DR) and 0.85 grams of 2,2′-azobis (2-amidinopropane) dihydro Chloride (Wako, Lot No. P2197) is dissolved in 2050 grams of water and added to the acrylic acid monomer in the resin kettle. The solution is sparged with nitrogen for 15 minutes to remove dissolved oxygen. The resin kettle is then sealed and the solution is heated at 40 ° C. for 16 hours.
[0244]
The resulting gel is allowed to cool and then crushed into pieces of about 1 cm diameter and dried in a vacuum oven at 55 ° C. for 60 hours. Using a Willy mill, the sample is pulverized and sieved through a USA 20 mesh sieve to obtain a uniformly crosslinked polyacrylic acid.
[0245]
(Ii) Preparation of anion exchange absorbent polymer-crosslinked polyallylamine
Polyallylamine, 1250 grams of 20% solution (Nittobo, Tokyo, Japan, lot number 80728) is weighed into a 2000 mL glass jar. Ethylene glycol ether, 19 grams of a 50% solution (Aldrich Chemical Company, catalog number E2,720-3) is diluted with 20 grams of distilled water and added to the polyallylamine solution. The mixture is stirred for about 2 minutes at room temperature prior to being placed in an evacuated oven at about 60 ° C. overnight.
[0246]
The resulting gel is crushed into pieces having a diameter of about 5 mm and dried in a high vacuum for about 96 hours to obtain a lightly cross-linked polyallylamine anion exchange absorbent polymer, which is stored in a dry atmosphere.
[0247]
(Iii) Mixed bed ion exchange absorbent polymer
The anion exchange absorbent polymer of cross-linked polyallylamine is ground and screened. Collect the particle size portion that passes through the USA series standard 25 mesh screen but does not pass through the USA series standard 70 mesh screen (ie, the portion containing particles in the range of about 200-700 micron diameter).
[0248]
About 125 grams of screened cross-linked polyacrylic acid (200-700 micron diameter) cation exchange absorbent polymer and about 125 grams of screened cross-linked polyallylamine anion exchange absorbable polymer are mixed together and mixed for each type of polymer. The particles were distributed uniformly throughout the mixture. This mixture constitutes the mixed bed ion exchange absorbent polymer composition used in the storage absorbent member of this example. Further information regarding such compositions can be found in US Patent Application No. (filed Mar. 1, 1999, Hird et al.) (P & G Case 7432—named “absorbing polymer composition with high adsorption capacity under pressure”). Which is already incorporated herein by reference.
[0249]
The capillary adsorption isotherm of this storage absorbent member is illustrated graphically in FIG.
[Brief description of the drawings]
FIG. 1 is an exploded view showing a diaper having an absorbent core including a storage absorption member having a high capillary suction capacity according to the present invention.
2a is an exploded view of a representative multi-layer core included in a diaper as shown in FIG.
2b is an exploded view showing another typical multilayer core included in the diaper as shown in FIG.
FIG. 3 is a photomicrograph (500 × magnification) of a representative high surface area polymer foam useful for the storage absorbent member of the present invention.
FIG. 4 is a photomicrograph of the large surface area polymer foam shown in FIG.
FIG. 5 is a photomicrograph of a storage absorbent member of the present invention comprising a particulate hydrogel-forming absorbent polymer and a particulate polymer absorbent foam.
FIG. 6 is a photomicrograph of a storage absorbent member of the present invention comprising a particulate hydrogel-forming absorbent polymer and high surface area cellulose acetate fibers.
FIG. 7 is a photomicrograph of a storage absorbent member of the present invention comprising particulate hydrogel-forming absorbent polymer and high surface area glass ultrafine fibers.
FIG. 8A is a diagram showing the configuration of an apparatus for measuring the capillary absorption capacity of an absorbing member.
FIG. 8B is an enlarged cross-sectional view showing the glass frit generally shown in FIG. 8A.
8C is an enlarged cross-sectional view of the glass frit cylinder / piston assembly shown in FIG. 8B.
8D is an enlarged cross-sectional view showing the appearance of the piston of the cylinder / piston assembly shown in FIG. 8C.
FIG. 9 shows capillary adsorption isotherms for various storage and absorption members of the present invention and a conventional member (shown as Comparative Example A) containing cellulosic fibers (fluff) and a hydrogel-forming absorbent polymer.
FIG. 10 is a block diagram of an apparatus for forming a representative storage absorbent member of the present invention, which member comprises a particulate polymer foam and a particulate hydrogel-forming absorbent polymer.
FIG. 11 is a block diagram of another apparatus for forming a typical storage absorbent member of the present invention.
12 is a perspective view of a storage absorbent member manufactured using the apparatus shown in FIG.
13 is an enlarged perspective view showing a part of FIG.

Claims (5)

A high capillary suction storage absorbent member comprising (i) separate hydrogel-forming absorbent polymer particles and (ii) separate hydrophilic fibers, wherein the fibers are glass ultrafine fibers, fibrillated Selected from the group consisting of cellulose acetate fibers, and mixtures thereof, wherein the storage absorbent member contains at least 25% fiber, based on the total weight of the member,
The storage absorbent member is one or more of the following:
a) Capillary adsorption / absorption capacity at 35 cm height of at least 8 g / g;
b) Capillary adsorption / absorption capacity at 50 cm height of at least 7 g / g; or c) Capillary adsorption / absorption capacity at 100 cm height of at least 4 g / g ;
Have a will, the
The storage absorbent member is
a) preparing a hydrogel-forming absorbent polymer;
b) preparing a fiber selected from the group consisting of glass ultrafine fibers, fibrillated cellulose acetate fibers, and mixtures thereof;
c) forming a suspension consisting of a hydrogel-forming absorbent polymer and fibers in a liquid, wherein the liquid is absorbed by the hydrogel-forming absorbent polymer below 5 g / g;
d) binding the hydrogel-forming absorbent polymer and fibers in the suspension;
e) removing the liquid from the suspension, thereby forming a dry structure of uniform moisture content comprising the hydrogel-forming absorbent polymer and fibers;
A storage absorbent member , characterized by being formed by a method comprising:   The storage / absorbing member according to claim 1, wherein the member contains at least 30% of fiber based on the total weight of the member.   The storage and absorption member according to claim 1, wherein the storage and absorption member has a capillary adsorption and absorption capacity at a height of 100 cm of at least 4 g / g. The member has a capillary absorption capacity at 0 cm height of at least 15 g / g and one or more of the following:
a) Capillary absorption efficiency at 50 cm height of at least 30%;
2. The storage absorbent member according to claim 1, having a capillary absorption efficiency at a height of 35 cm, at least 50%.   An absorbent product comprising the storage / absorbing member according to claim 1.

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